Last Month's OPAG Meeting

The presentations for last month's meeting of NASA's Outer Planets Assessment Group (OPAG) were posted online last week.  The focus of the meeting, which took place on February 8 and 9, was the president's NASA budget for FY2011 and the projected budgets over the next few years, and the Europa/Jupiter System Mission (EJSM).

In the first day of the meeting, the presenters focused on the new NASA budget and the ongoing, planetary science decadal survey.  James Green and Curt Niebur, both from NASA Headquarters, presented on the new budget and how it impacts ongoing and upcoming outer planet missions.  Green made it clear that NASA's Planetary Science Division was committed to funding EJSM through at least pre-phase A, and the budget reflects that.  NASA will then look to the new decadal survey for how to proceed with flagship mission program.  Personally, I don't see why they need to wait, the flagship mission was selected competitively.  I don't see why we need to go through this non-sense again.  These issues won't effect budgets until the out-years in the current budget projections...  Anyways, Green also reported that funding for the restart of Pu-238 production is back on track now that NASA and the Department of Energy have developed a plan outline the "role and contribution of major users of Pu-238", as requested by Congress last year after nulling out such restart funding in last year's budget.  Niebur's presentation provides a breakdown of planned funding for EJSM in the president's budget: "FY11: $20M, FY12: $72M, FY13: $64M, FY$14: $53M, FY15: $63M."  This is fine for phase pre-A and A, but as we get passed instrument selection from the AO, those budgets should be going up not down, as seen now in FY13, FY14, and FY15, if a 2020 launch is still planned for.  John Spencer's presentation on the satellites part of the decadal survey showed a series of mission concepts that are being evaluated inclusion in the survey, including a New Frontiers-class Io Observer.

The Europa/Jupiter System Mission presentations from the meeting's second day provide additional details on cooperative observations by the two spacecraft of the mission.  For example, they plan to use a radio link between the Jupiter Europa Orbiter and the Jupiter Ganymede Orbiter to probe the upper atmosphere of Jupiter. 

I will post more on the EJSM presentations tomorrow.

Budgets, Carnivals, and Cryovolcanoes, Oh My!

Here are some short little news items that are hitting the interplanetary interwebs today:

• Ian Musgrave's Astroblog is this week's host for the Carnival of Space, #142 of its name.  The Carnival of Space is a collection of links to the best space blog posts from the week that was.  In this edition, learn about the launch of the Solar Dynamics Observatory, the (then) ongoing STS-130 shuttle mission to install the Cupola at the International Space Station, and why the oxidation of iron creates a positive spectral slope in the visible (aka, "Why is rust red?").
• Today, the Cassini Imaging and the Composite Infrared Spectrometer (CIRS) teams released a series of images from the November 21 encounter with Enceladus, a cryovolcanically active moon of Saturn.  This set of images includes some awesome mosaics, including one showing a series of water-rich jets erupting from fractures within the moon's south polar region and another combined with CIRS data to show thermal emission from one of these fractures, Baghdad Sulcus.  Also don't forget to check out two mosaics of Enceladus' leading hemisphere, an area not seen at high-resolution previously, and an 3D anaglyph (don't forget your red-blue 3D glasses) of a portion of Baghdad Sulcus.
• Yesterday, NASA released further details on its proposed budget for the next fiscal year, FY2011, including the breakdown for Planetary Science.  Overall, the next year will see budget increases for the Planetary program with out-years showing shallower increases, that according to Van Kane, would barely cover inflation, possibly decreasing the budget's purchasing power. The Mars program and precursor missions (mostly Lunar) will see major increases, with more modest increases over the five projected years for the Outer Planets Program (Cassini, EJSM, and ROSES, a research grant program).  Until FY2013, the budget is inline with the project needs of the Europa/Jupiter System Mission for its Phase Pre-A and A when studies will be conducted to mitigate the radiation risk further, instruments selected using an Announcement of Opportunity, and the preliminary concept design finalized.  Starting with Phase B in FY2014, the budget does start to deviate from what is required for JEO, staying in the $150 million range when it should closer to $300 million (or $425 million if one includes reserves) in FY2014 and $400 million (or $600 million if one includes reserves) in FY2015.  While a bit discouraging, keep in mind that budget projections for years so far out are...very sketchy.  I don't trust them any farther than I can throw them; who knows who could be in the White House at that point.

Link: Carnival of Space #142 [astroblogger.blogspot.com]
Link: Enceladus Rev121: Forest of Jets [ciclops.org]
Link: FY11 NASA Budget Proposal Details [futureplanets.blogspot.com]

Animation of the Jupiter Europa Orbiter's Four Io Flybys

Yesterday, while finishing up work on the Exploration of Io article on Wikipedia and looking for a graphic for the Jupiter Europa Orbiter (JEO), I noticed that a SPICE trajectory file for JEO had been posted online. The Jupiter Europa Orbiter is NASA's portion of the Europa/Jupiter System Mission approved last year. I can use the SPICE kernel to display the position of the spacecraft at a given time in Celestia.  The trajectory file covers the Jupiter tour portion of the current mission baseline, though obviously a number of factors between now and the arrival of JEO at Jupiter will cause changes to this baseline, including changes in the launch date (assumed as February 2020 with an arrival at Jupiter in December 2025).  So, as of right now, these provide more of an example of the types of flybys JEO can perform at Io.

I've created a little video and uploaded it to Youtube with animations from Celestia simulating each of the four Io flybys in the current tour.  You can see some of the highlights from each encounter, though note that no science is planned for the first encounter (Io-0) as it takes place right before JEO's all-important, Jupiter Orbital Insertion burn.  For Io-1, on July 9, 2026, JEO passes almost directly over the Amirani plume, and depending on how high gases from the volcano reach, it could directly sample the composition of it.  JEO can also image the north polar region of Io from an oblique angle. However, Amirani's plume is ~75 km tall, while the altitude for Io-1 is 300 km.  For Io-2, on September 3, 2026, JEO should be able to image the Pele volcano and south polar region at high resolution. In the latter case, this is the section not covered by Voyager 1 at medium resolution.  The Zamama, Marduk, Prometheus, and Pele plumes will also be visible along the bright limb near C/A.  Finally, for Io-4, JEO will pass directly over Tohil Mons providing a chance to obtain laser altimetry over a mountain we have pretty good stereo coverage already, providing a useful comparison.

I wrote up a more detailed article on the potential science from each of these encounters last February.



I hope you all enjoy!  I should point out that this video was uploaded at 720p so you can view it in high-definition, and this definitely works better if you view it full screen.

Link: Animation of the Jupiter Europa Orbiter's Four Io Flybys [www.youtube.com]

Carnival of Space #139 and the FY2011 NASA budget

The 139th edition of the Carnival of Space, a weekly series highlighting the best in the astronomy and space blogosphere, is now online at Mama Joules, a kid-friendly astronomy blog.  You know the drill.  Some great posts on orbital terminology, the premature reports of Spirit's demise, and early reports of the President's NASA budget for FY2011.  Gotta love the white board drawings illustrating the concepts of "gravity" and "flyby".

Speaking of the President's NASA budget for FY2011 (10/2010-10/2011), it was released today and a number of my fellow bloggers have commented about it including Van Kane and Phil Plait.  For information from the horse's mouth, check out this presentation from the NASA website, the NASA FY2011 factsheet from the Office of Management and Budget website, and the more detailed budget breakdown on the OMB site (though its breakdown is less helpful, IMHO).  For me this budget is a mix of good and bad.  Let me be clear there is a lot of good in this budget, though of course that assumes you trust the out-year budget estimates...  I like the precursor mission concept.  This could put some of the Mars, Moon, and near-Earth asteroid exploration from the Science Mission Directorate to the Exploration one, increasing the amount of money available for other targets.  The budget increases for space technology and extends the lifetime and capabilities of the International Space Station, which I support.  While the space station wasn't very popular when it was started, now that it is near complete, the ISS represents an important asset in space and we should use it for as long as we possibly can.  The ISS should be in use until we are basically holding the thing together with duct tape, a la the Mir space station.  The earlier plan to abandon the station in 2016 would have turned the ISS into an even larger waste of money.

Finally, the planetary science budget, which controls how much money all of your favorite missions in progress (Cassini, New Horizons, MER, MRO) and in construction (EJSM) get, increases by $140 million in FY2011 compared to this year's budget.  Looking at the out-year projections, the budget could increase by a $164 million between FY2011 and FY2015, but again, out-year projections are generally just guesstimates of future budgets, and should be taken with a GIANT grain of salt.  However, the NASA presentation does make it clear that they intend to use this money to restart Plutonium-238 production, essential for outer-planet missions, as well as continue operations for existing spacecraft like Cassini and funding for the Europa/Jupiter System Mission (EJSM).

Now, for the bad...  The budget cancels the Constellation program which include new heavy-lift rockets like Ares and crew vehicles like Orion to replace the shuttle.  This program was intended to support future manned missions to the Moon and Mars with a focus on long-term habitability as opposed to the Apollo-like short trips.  This program will be replaced by a combination of funding for commercial ferries to the space station and technology development to get the technologies in place to go to the Moon.  The good news is that this would shorten the time NASA would need to rely on Russia to get to the International Space Station following the Space Shuttle retirement from 5 years to 2-3 years with some cost savings.  However, I am concerned that it will be more difficult to maintain the out-year budget increases for science if federalized manned spaceflight is cut, as NASA could lose some its protection from powerful senators from Texas and Florida.  Then again, Constellation, with its payoff not coming for another five years, has always been a budgetary target, and it really comes as no surprise that Obama would cut it.  After all, George W. Bush proposed it, and since he was evil, Constellation must be a bad idea... Wait, that makes no sense...

In conclusion, I like the budget increases we are seeing for the planetary science budget, particularly the restart of the plutonium-238 production (though that was also proposed last year by the President, but got shot down by Congress).  However, I believe that the cancellation of Constellation and the move from a federal manned spaceflight program to a privatized one will make the projected out-year budget increases more politically vulnerable.

Link: Carnival of Space #137 [mamajoules.blogspot.com]
Link: NASA Fiscal Year 2011 Budget Estimates [www.nasa.gov]

OPAG Spring Meeting Presentations

Well, Hey Hey all! You've probably been wondering where in the world I have been. Well, I have been around, but unfortunately there hasn't been much news lately, and I've been spending my free time playing Europa Universalis III rather than processing Io images. Sorry, but it is true. I think it was time well spent. I just conquered Constantinople. I feel rather proud of myself. So I haven't abandoned you all. I will try to post more often. I'm sure there are scraps of news I've missed.

Anyways, the presentations from the OPAG Spring Meeting are finally online. Yes, Hell has frozen over. Or maybe that was Europa. Wait, that's redundant, scratch that... I kid, I kid. NASA's Outer Planets Assessment Group (OPAG) held their spring meeting in Bethesda, Maryland last month and we have been waiting for the presentations to get posted online. Not just me, but Van over at Future Planetary Exploration has been waiting.

Two presentations caught my eye. The first is by my advisor, Alfred McEwen, and covers the Io Volcano Observer. This presentation covers much of the same terrain that we saw in the presentation given in December at the Io Workshop, but it also goes into further details over a possible tour plan and the science goals. The example tour presented includes some info about how the IVO team might plan the mission. The sample tour includes no flybys with altitudes less than 291 km in altitude, but the previous slides does point out that the do plan to try closer encounters, down to 100 km, later in the nominal mission and extended mission. Closer encounters are particularly important in order to observe small scale features on the surface (like skylights) and to use the mass spectrometer within an active plume. The sample mission assumes a different launch from the nominal January 2015 one, so again, take the sample tour with a grain of salt. Still, it would seem that the tour designers want to keep the sunlit region on Io during the flybys fairly similar, but not so similar that only half the surface would ever be visible during these encounters.

The IVO presentation also concentrates on the science objectives for the mission. These mission objectives largely cover those proposed for the Io Observer mission type available for the New Frontiers-3 announcement of opportunity (but all but impossible because NF-3 can't use radioisotope power sources). These science goals include (level 1 goals in bold):

• Understanding the eruption mechanisms for Io's lavas and plumes and how these compare to similar processes on Earth and other terrestrial planets
• Determining Io's interior structure, particularly the melt fraction of the mantle
• Determining the properties and mechanisms of Io's tidal heating and implications for the orbital evolution of Io and Europa
• Investigating the processes that form Io's mountains and other tectonic structures in the satellite's high heat flow environment
• Understanding Io's atmosphere and ionosphere and their connection to Io's volcanism
• Determining whether Io has a magnetic field
• Understanding Io's surface chemistry, including volatiles and silicates
• Improving our understanding of Jupiter system science

The IVO team feels that this mission along with the Jupiter Europa Mission, would go along way toward responding toward these goals, though many require a high data rate as a result of the fast encounters, so a large amount of data storage will be needed (~20 Gb) in order to capture all the close approach data, particularly from INMS and RCam. McEwen also stresses the synergy between JEO and IVO, making it clear that even with the Europa/Jupiter System Mission having been selected, the Io Volcano Observer will still be needed by the Io community, as it provides much more information about the polar regions, particuarly the heat flow up there, and would provide much more data on the composition of Io's lavas. Finally, IVO would help to mitigate EJSM's risk by testing the ASRG, the next generation of radioisotope power source to be used by IVO, if EJSM uses them as well.

Curt Niebur gave a presentation on the results of the Outer Planets Flagship Mission selection process. Niebur goes into detail the rationale behind the Selection Panel's decision to give higher priority to the Europa/Jupiter System mission for the next decade flagship mission. Basically, as has already been reported, the EJSM concept was seen as been more technically mature, the result of several prior mission studies over the last decade for a Europa follow-on mission to Galileo. Niebur notes several issues with the Titan concept, but the technical review basically noted that technical issues and design drivers many of the mission elements, such as the SEP stage development, the thermal subsystem, the integration of the in situ elements, and aerobreaking where not realistically reflected in the budget estimate.

Link: OPAG Spring Meeting Presentations [www.lpi.usra.edu]

Notes from the Surface of the Sun

Sorry for the lack of updates the last couple of days. The air conditioner at home is STILL out, though I am told it should be back up and running tomorrow. Unfortunately, while many of you out east are getting lovely, lovely snow, it was 92°F here. This kinda limits my mental functioning during non-work hours (by work hours, I mean, times when it isn't broiling hot in here).

So while I wait for them to get back to working on my A/C, here is a neat video about the EJSM. Io gets a short mention at 2:33 in with a simulation of the I4 flyby (with a plume at Malik...).

Paul Schenk on the OP Flagship Selection

Paul Schenk, a planetary scientist from the Lunar and Planetary Institute in Houston, Texas, has a nice post on Unmannedspaceflight.com with his thoughts on last week's EJSM selection. I agree with what he said there, for a lot of planetary scientists, there is a lot that can be done in the Jupiter system, and as he mentions, in the wake of Galileo's successful failure, there is a lot that needs to be done in terms of Jupiter science.

For those who would have preferred the Titan mission, come on, you got EIGHT more years to hopefully look forward to from Cassini. Check out John Spencer's post on the Planetary Society Blog for more info on all the craziness that will happen with Cassini during its Extended-extended mission. The XXM includes 56 flybys of Titan and 12 flybys of Enceladus. I mean, that's more than we have done up to this point. To be honest, I also get excited about the flybys of the little rocks. Maybe it is the excitement of seeing a new world upclose that I've kinda lost from seeing Titan, Dione, Enceladus, etc. images all the time. We got a flyby of the small moon Helene coming up next March during the first extended mission, and during the XXM we have another one of Helene (providing coverage of the unilluminated hemisphere from the first Helene flyby) as well as flybys of Telesto and Methone. So while Titan will not get a flagship mission until the 2025-2035 time frame, the next decade will still be a great time to do Saturn system research.

Right above Paul's post over at UMSF, Ted Stryk posted his version of a partial color frame from Galileo's I27 flyby showing Pillan, Reiden, and parts of the Pele plume deposit. I should probably process my own version of that. That is definitely on my To-do list for tomorrow evening.

Link: Paul Schenk's post at UMSF.com [www.unmannedspaceflight.com]

Outstanding Science Questions at Io

Eric posted a few comments yesterday which provided a great suggestion for a blog post. What are the outstanding science questions that remain following Galileo and New Horizons? Can these questions be answered by the Jupiter Europa Orbiter (and Io Volcano Observer)? While better understanding Io's potential habitability by native lifeforms is certainly not one of them, there are at least five I can list here.

Before I do that, I want to point out Van Kane's post on his blog giving some of his closing thoughts on the Flagship mission selection. He pointed to my last post on how the selection of Europa as the target for that mission might effect the Io Volcano Observer and noted that the instruments could be more finally tuned to better answer questions at Io. That idea has crossed my mind. If the cost of IVO can't be brought in line with the Discovery mission cost cap, one potential alternative is to submit beefed up versions of some of IVO's instruments, particularly RCam and the Thermal Mapper, for the JEO Instrument Announcement of Opportunity. RCam's radiation-hard color push-broom camera could be just as effective at observing small-scale features on Europa as it could for determine eruption temperatures on Io. Additional bandpasses on Thermal Mapper compared to the Thermal Imager in JEO's model payload could also be useful for Jupiter on JEO. However, you do still lose the spatial coverage that would be provided by IVO, which would help it be more robust against variability in Io's volcanic activity. For example, what if Amirani was inactive in the mid-2020s?

So with that out of the way, here are five of the top (in my mind) outstanding science questions at Io:

1. What is the composition of Io's lava's?
2. What is the typical eruption temperature for Io's volcanoes? These first two questions are quite related. Following Galileo, there was consensus that Io's primary lavas were composed of basalt, a silicate lava rich in iron and magnesium and common on the terrestrial bodies in the solar system. However, the exact composition was very poorly constrained by the available data (dark at visible wavelengths, an absorption at 1 micron consistent with iron, and estimated lava temperatures in mafic to ultramafic range). The eruption temperature could be related to the amount of partial melting in Io's mantle. And of course temperature is related to the composition of Io's lavas. Generally the higher the magnesium level, the more mafic it is, the greater the liquidus temperature (and thus the eruption temperature). Understanding the effect of superheating during the ascent of the magma is also important. These questions can be answered through the measurement of Io's thermal emission in the 0.7-1 micron range (like from a near-infrared spectrometer or RCam on IVO) and by looking for absorption and emission features in the near-infrared that are consistent with materials in Io's lava, such as the Christiansen Feature.
3. Is tidal heating on Io steady-state or time-variable? One of the potential implications of measurements of Io's heat flow is that Io may be pumping out more heat from its interior than it currently receives from tidal heating as a result of its orbital resonances with Europa and Ganymede. This would indicate that Io is cooling down from a period of much greater tidal heating in its past. A potential way to test this is by high-resolution tracking of the position of Io and Europa over time. One of the mission goals for JEO is to provide this kind of tracking to better constrain the orbital evolutions of Io and Europa. IVO's polar orbits would allow for better thermal emission mapping of Io's polar regions, which are thought to be much warmer than they should be given the lower solar angles.
4. How are Io's two major structural landforms, paterae and mountains, formed? Various models following Voyager and again after Galileo have been produced to explain how paterae and mountains form on Io. Sub-surface radar sounding and high-resolution, low sun imaging could go a long way toward looking at the tectonic mechanisms behind how these intriguing features are formed. JEO would provide the sub-surface sounding, while IVO (and JEO to an extent, but longitude coverage would be limited) could provide imaging of a variety of mountains and paterae.
5. Does Io have an internal magnetic field? This question may have been answered as a no by Galileo, but closer encounters at different latitudes with a magnetometer-equipped spacecraft would help put this issue to bed. Understanding Io's magnetic environment would help with our understanding of Io's deep interior.

Obviously, there are certainly more than just these five. These five also reveal my geology bias as there are certainly a lot of remaining questions regarding Io's interaction with Jupiter's magnetosphere and about Io's atmosphere.

How EJSM affects the Io Volcano Observer

With a mission now planned for the Jupiter system in the 2020s, how will the Io Volcano Observer proposal be affected? Would a dedicated Io mission even be necessary?

The Io Volcano Observer and the Jupiter Europa Orbiter would conduct complimentary science. Both spacecraft have high-resolution cameras capable to studying Io's surface in fine detail during flybys as well as monitoring Io's global volcanic activity from a distance. Both can conduct mass spectroscopy of Io's atmosphere and plumes as well as observe Io's thermal inertia. The Jupiter Europa Orbiter would be capable of acquiring observations not currently in IVO's baseline payload such as near-infrared spectroscopy, ground-penetrating radar, laser altimetry, and particle and plasma analysis. So seemingly, the Io Volcano Observer would not be necessary. Not so fast.

The Jupiter Europa Orbiter's instruments are designed to study Europa, with bandpasses of the various instruments and their functionality driven by that requirement. Studying the other bodies in the Jupiter system, while a level 1 science requirement, really is just gravy for the mission. JEO's unique instrumentation, such as the Ground-penetrating radar, can answer quite a few questions that IVO can't. However, the design of the payload for IVO has been defined to specifically answer questions at Io. For example, the camera on IVO would be capable of observing volcanic activity with multiple filters with less than 0.1 seconds between color frames. This allows fairly accurate measurement of the lava temperatures at Io's volcanoes. This can constrain the amount of partial melting in the mantle needed to support the eruption temperature observed. The band passes on the Thermal Mapper, rather than being selected to search for warm spots on an icy world, will be selected to explore different volcanic processes on Io of different ages as well as looking at the silicate composition of these flows.

Also, don't forget that IVO will perform at least seven Io flybys during its 1.5-year primary mission (starting in early 2021), three more than the encounters planned for JEO. In addition, IVO has enough margin in its radiation shield to support seven more encounters, which could be spaced out by as much one year apart to help study the long-term life time of IVO's power source, the two Advanced Sterling Radioisotope Generators (ASRGs). This extended mission could help fill the gap between IVO's primary mission which ends in late 2022 and JEO's arrival in late 2025. This provides the potential for spacecraft monitoring of Io covering almost eight years, similar to Galileo's time at Jupiter.

While the Jupiter Europa Orbiter will perform quite a bit of science at Io, since the instruments are not optimized for Io science, there is still a need for a dedicated mission like Io Volcano Observer. Potentially JEO could allow IVO to trim some costs by reducing some of the redundancy, like the magnetometer instrument. However, the priority for an Io mission may go down in comparision to other potential Discovery-class missions with the EJSM arrrive only a five years later than IVO.

Roundup of News Articles about EJSM

Quite a few news articles have been posted online about the selection of the Europa/Jupiter System Mission as the next Outer Planet Flagship Mission. Many of these report on a telecon between NASA officials and a few members of the press yesterday about this announcement. Perhaps the most interesting new news from this telecon is that the flagship mission is currently not fully funded (though budget projection in the last year have taken into account the flagship mission), though according to Space.com, "NASA is setting aside about $10 million to continue studying design challenges for its Jupiter Europa orbiter."

• Russia, Europe and NASA explore ocean depths of Jupiter’s Europa from the Russian website Pravda. Looks like the Russians are continuing to push their desire to send a lander to Europa.
• It's all systems go for Europa from the Los Angeles Times. The article focuses a bit on the local angle via the Jet Propulsion Laboratory.
• NASA Puts Money on Mission to One of Jupiter's Moons from the Washington Post
• Bold New Missions to Jupiter and Saturn Planned from Space.com
• Europa Selected As Target of Next Flagship Mission from Slashdot (yeah my first approved slashdot article)
• Europa wins next big planetary mission from Nature
  

What's next for the Europa Jupiter System Mission

The news of the Outer Planet Flagship downselection is beginning to reverberate across the internet and planetary science community. Jim Green, the directory of the Planetary Science Division at NASA, has posted a message to the Science Community on the OPF website. The Planetary Society has also issued a statement on this announcement. You can check that out on Emily Lakdawalla's blog. Also, check out the thread on at UMSF if you wish, though feel free to leave a comment here with your reaction to this news.

Now that the Europa Jupiter System Mission has been selected, what's next for a mission whose launch (nominally) doesn't take place for another 11 years?

Pre-Phase A
Starting today (or last year about this time, depending on how you look at it), EJSM enters Pre-Phase A. Spacecraft development is generally defined in different stages, or phases, of progress, running from Phase A through Phase F. During Pre-Phase A, mission planners will be looking to further refine the mission concept and working on risk mitigation. From now until January 2011, work will be performed on further defining the mission goals of the EJSM, though the Final Reports states that since so much has gone into defining the goals of a Europa mission already, these are not likely to change. Neither are the definitions of the types of instruments that will be needed, though further refining maybe needed in the run up to an instrument Announcement of Opportunity, to be released by NASA in December 2010. So, the majority of the planning work over the next two years will be performed on risk mitigation, particularly with respect to planetary protection and radiation-hardening. Planning done now could be used to save money in the future (particularly in Phase A) and help reduce the chance for cost over runs.

For the Jupiter Ganymede Orbiter, that spacecraft is now in the running for the European Space Agency's Cosmic Visions L-class mission. That's right, despite this downselection, the contest isn't over for JGO. Though JEO is safe, it was selected and it enters Pre-Phase A. The Jupiter Ganymede Orbiter will be squaring off against two astronomy missions: XEUS, an X-ray telescope that will search for black holes and examine the structure of clusters of galaxies, and LISA, a constellation of three spacecraft that will act as a gravitational wave observatory. As currently outlined by ESA, the three missions will be narrowed down to two in October and November of this year. These two missions will then be in a "competive definition phase" during 2010 and 2011, with the downselection to one mission taking place in November 2011. Even then, the decision to proceed with the selected mission "will depend on the financial situation of the programme." So the Jupiter Ganymede Orbiter has a long road ahead of it.

Phase A
During the next stage of development, Phase A, the instruments will be selected and reviewed. According to the final report, a NASA Instrument Announcement of Opportunity is planned in December 2010 with proposals due in March 2011 and payload selected in September 2011. Keep in mind that the instruments outlined in the various reports published for this concept study were model payloads, basically providing a rough idea of what the mission team is looking for out of a particular instrument. Further refinements during Pre-Phase A could obviously change what they are looking for. For example, the mission team may want different frequencies for the Ice-Penetrating Radar than what is outlined in the Final Report. Phase A ends once all the instruments have been selected, reviewed, and approved by NASA HQ.

Looking Forward
With the end of Phase A expected in October 2013, the moves on to the the other phases. During Phase B, which will run about 20 months from October 2013 through June 2015, more detailed designs will be developed for both the spacecraft and the various parts of the spacecraft with preliminary design reviews in late 2014 and early 2015. In Phase C, running for 30 months from June 2015 through December 2017, the various parts and instruments will go through one final review in late 2015 and early 2016 before actually being built. Software and avionics will be developed and integrated and the mission plan and trajectory will start to reach a final state. In Phase D, the various parts and instruments will actually be assembled into a working spacecraft in early 2018. This will be then be followed by rigorous testing to make sure all the spacecraft's parts are working the way they should be and that the spacecraft can handle launch and the environment of space. Finally JEO will be delivered to Kennedy Space Center in Florida in August 2019 and from there it will be launched on a Atlas V in March 2020.

So, now the real work begins (and that was just a very coarse summary above).

EDIT 02/19/2009 1:40am: Corrected the launch vehicle from Delta IV to an Atlas V. Sorry about that.

Europa/Jupiter System Mission Selected!!!

Of course NASA just wants to mess with me, you know that right ;) No sooner do I post a note about how the Flagship mission hasn't been announced, the flagship mission is announced. And the winner is:

The Jupiter System!

This morning, NASA HQ announced the decision to proceed with the EJSM over the Titan option. You can read the announcement press release over at NASA's website. As to the why, predictably it came down to technological readiness:

NASA and ESA engineers and scientists carefully studied both potential missions in preparation for last week's meeting. Based on these and other studies as well as stringent independent assessment reviews, NASA and ESA agreed that the Europa Jupiter System Mission, called Laplace in Europe, was the most technically feasible to do first. However, ESA's Solar System Working Group concluded the scientific merits of this mission and a Titan Saturn System Mission could not be separated. The group recommended, and NASA agreed, that both missions should move forward for further study and implementation.

Basically, they felt the Europa mission is ready to fly now, but the Titan mission should not just be shelved, so look for the Titan people to make a big push during the next flagship mission opportunity.

I will have more in a few hours. In the mean time, for more analysis on the EJSM, check out the Flagship Mission section of this blog.

Tip of the hat to Van Kane.

Link: NASA and ESA Prioritize Outer Planet Missions [www.nasa.gov]

Flagship Mission Selection Still Not Announced

Presumably a lot of you are coming here to check on which target, Titan or Europa, was selected for the next Outer Planets Flagship Mission. Despite the fact that the Downselection meeting was supposed to have taken place last Thursday, as of the time of this post, still no word yet on the outcome of that meeting. Not sure what the delay is all about, so hopefully it will be announced in the next few days.

Looking at the calender, there is an Outer Planets Assessment Group (OPAG) meeting on March 9 and 10 in Bethesda, Maryland. OPAG is a committee that advises NASA's Planetary Science Sub-Committee (PSS) on issues related to the exploration of the outer solar system. Presumably, the downselection panel's findings should be announced before that meeting. So that's taking a look at a worst-case scenario for those (like me) who are waiting quite impatiently.

In the mean time, check out this piece of Europan propaganda, I mean this informative video on Europa (stupid...alliance, the video makes fun of Io...must destroy...). Anyways, sorry there, Dr. Strangelove moment... Check out this video on Youtube from the Discovery channel. Still, that guy called Io ugly!!!

Also, don't forget to check out Van Kane's discussion of the Titan Montgolfière and lake lander over at his Future Planetary Exploration blog.

The Thickness of Europa's Ice Shell from JEO

Okay, after I saw Emily practically dare me to talk about something other than Io with respect to these flagship missions, I thought fine, I will break my one rule here and talk about...Europa. Cue dramatic prairie dog! In particular, I want to look at perhaps one of the most important science goals for the Europa/Jupiter System Mission: determining the thickness of Europa's water-ice shell.

Following the Galileo mission, the Europa scientists were split into two armed camps: those that felt that the evidence found by Galileo indicated that Europa had a thick ice shell (read: the ocean did not "communicate" with the surface) and those that thought Europa had a much thinner ice shell (read: the ocean did "communicate" with the surface). Okay, they weren't literally armed, though I hear they had to put metal detectors at the entrances to the Europa sessions at LPSC. In the thin ice case, the ice shell would be on the order of a few kilometers thick (Greenberg et al. 2000), while in the thick ice case, the ice shell would be 10 to 30 kilometers thick (Pappalardo et al. 1999). Knowing the thickness of the ice shell is important for understanding Europa's habitability as well as designing a future submarine that might explore the ocean beneath. Obviously digging through two km of ice is quite a bit different from digging through 30. Knowing the thickness of the ice shell is also important for understanding Europa's surface geology. With a thin shell, chaotic terrain and double ridges can be explained by break-throughs of the crust by the underlying water ocean. With a thick shell, these features are better explained by a convecting ice layer producing diapirs, which imping on the surface.

While in orbit around Europa, the Jupiter Europa Orbiter would use four primary measurements to constrain the thickness of the ice and water shells: gravity and topography measurements, radar sounding, and magnetometer data. In a previous post, I reported on the types of science the Ice-Penetrating Radar can obtain at Io, but the instrument's primary purpose is identifying shallow water pockets and detecting the ice-water interface at Europa. The ability of the IPR to detect the ice-water interface can vary depending on a number of factors. For example, in the thick ice case, the ice shell is expected to be split into an upper, brittle cold ice layer and a lower, ductile warm ice layer. The warm ice layer has a much higher dielectric constant, and this would reduce the penetration depth of the radio signal IPR transmits. Heavy fracturing of the ice layer can also reduce the penetration depth. Using a tectonic models, the team reports that penetration depths of 15 km are expected. The study team thinks that even a non-detection of the ice-water interface with IPR can be useful as a lower bound. Magnetometer measurements can be used to constrain the thickness of the water ocean by measuring the strength of the induced magnetic field at Europa.

Another pair of measurements of the ice shell thickness are gravity and topography. This requires the use of the antenna for Doppler tracking and the Laser altimeter for altitude measurements. These would be used to derive Europa's Love numbers, h₂ and k₂. The Love number h₂ is dependent on the tidal deformation of Europa's surface and can be measured by calculating the difference between laser altimetry of the same point on the surface at different times of day. Combining the two Love numbers can constrain the thickness of the ice shell as these numbers are a function of the rigidity of the shell.

Based on the measurements acquired by the Jupiter Europa Orbiter, the thickness of Europa's water ice shell can be constrained and the thick and thin water ice shell debate should be settled. However, depending on the thickness of that shell, it maybe difficult to derive a specific value for its thickness. The Ice-Penetrating Radar may not be able to see the ice-water interface if the shell is thicker than 15-30 km, which would be expected from the thick ice shell interpretation. If the shell is more on the order of less than 10 km, the ice thickness should be pretty well determined.

Io Science with the Jupiter Ganymede Orbiter

In my previous articles on the Europa/Jupiter System Mission, I have focused on the kinds of science that the Jupiter Europa Orbiter (JEO) can gather at Io, and rightly so. Of the two components of the mission, JEO will be the probe that will flyby Io, perform high-resolution science observations of that satellite. In addition, only the Jupiter Europa Orbiter has a narrow-angle camera capable of studying Io's geology and surface changes with spatial resolutions of better than 10 kilometers per pixel during most orbits during the Jupiter tour segment for that spacecraft, and while in Europa orbit. But can the ESA-supplied Jupiter Ganymede Orbiter still provide useful science at Io, even though it never comes within 650,000 km of Io? Let's delve a bit into the ESA Assessment Report for JGO to find out.

The Jupiter Ganymede Orbiter (JGO) is a solar-powered space probe designed to study Jupiter's two outer Galilean satellites, Ganymede and Callisto, extensively. To reduce the radiation dosage that could harm the solar panels, JGO never approaches Jupiter from closer than Ganymede's orbit. So, during the Jupiter tour phase of that probe's mission, from JOI on February 4, 2026 till GOI on May 22, 2028, spends its time flying by Ganymede and Callisto repeatedly. To support Callisto science, JGO will spend a year from February 2027 to February 2028 in a resonant orbit with Callisto, which allows the probe to encounter the moon 19 times. In May 2028, JGO goes into orbit around Ganymede, first in an elliptical 200x6000 km orbit, then in a circular, near-polar, 200-km altitude orbit. JGO would finally be crashed into Ganymede on February 6, 2029.

To support the science goals at these two icy satellites, JGO will carry a similar complement of instruments as the Jupiter Europa Orbiter, with a few exceptions. Like JEO, the Jupiter Ganymede Orbiter will carry an ice-penetrating radar, wide- and medium-angle cameras, a mid-infrared thermal mapper, a visible/near infrared imaging spectrometer, a laser altimeter, and an ultraviolet imaging spectrometer. Unlike JEO, JGO is not currently outfitted with a narrow-angle camera or an ion and neutral mass spectrometer, though the NAC is at the top of the JGO team's wish list. The NAC was dropped from the initial spacecraft baseline payload so the pointing accuracy needed for the spacecraft could be reduced, which helped to reduce JGO's cost. The Jupiter Ganymede Orbiter would carry a sub-millimeter wave sounder which would be used to better understand the dynamics of Jupiter's stratosphere and to measure local wind speeds and temperatures on Jupiter. This helps fill in gaps in our knowledge of Jupiter's atmosphere left behind by Juno.

Lacking a narrow-angle camera and with JGO never coming closer than 650,000 km of Io during its mission, what kinds of science could we possibly expect from the Jupiter Ganymede Orbiter? In terms of direct imaging of Io's surface, the best instrument might be the visible and near-infrared imaging spectrometer (VIRHIS). From Ganymede's orbit, the VIRHIS instrument would have a spatial resolution (using its high-spatial resolution mode at wavelengths between 400-2200 nm) of 81-185 km/pixel. This would allow JGO to monitor Io's volcanic activity at spatial scales comparable to the NIMS instrument during Galileo's primary mission of 1996-1997. VIRHIS could also be used to investigate the distribution of SO₂ across Io's surface. In combination with a similar instrument on JEO, during the Jupiter Tour phase, this would allow more continuous coverage of Io's volcanic activity as JGO could observe Io while JEO was near apojove, and vice versa. JGO could also observe Io when JEO is more intensively observing Europa during the satellite orbital stage. The medium-angle camera on JGO could observe Io at pixel scales of 165-375 km/pixel, which is comparable to Hubble. These pixel scales are not as useful for surface science (not at visible wavelengths anyway), and might be more useful for "Kodak Moment™" shots in conjunction with Jupiter or the other Galileans. The Thermal Mapping can also observe Io's thermal emission at longer wavelengths, but at a peak resolution from Ganymede orbit of 325 km/pixel.

Both the JEO Final Report and the JGO Assessment Report discuss the potential for synergistic science between the two orbiters, such as at Io. For example, while JEO is encountering Io, JGO could observe Io from a distance, focusing on the state of the Io Plasma Torus (observing the structure using JGO's ultraviolet imaging spectrometer) and the state of Io's atmosphere. These observations would help to put the Europa Orbiter's in-situ data in context. In another example, while JEO monitors a major volcanic eruption on Io and its effects on the plasma torus, JGO could look for effects on the Jovian magnetosphere as a whole. While Io is in eclipse, the two spacecraft could observe Io's plasma interactions in three-dimensions. Low-spatial resolution observations of Io from JGO could also help to increase phase angle and longitude coverage of bolometric albedo measurements, which can help to constrain Io's thermal inertia and from there heat flow. Finally, JEO and JGO could link up to acquire radio occultations of satellite atmospheres, such as Io's. This would allow scientists to probe Io's night-side atmosphere for example, which would be impossible simply using a direct-to-Earth link for a radio occultation except for near dawn and dusk. The JEO Final Report suggests that the two spacecraft could also be used to acquire stereo coverage of Io's plumes, but without a narrow-angle camera, such observations may not be possible (or as useful).

While the Jupiter Ganymede Orbiter, the European Space Agency's contribution to the EJSM, would not come very close to Io because of the high-radiation environment, the instruments onboard JGO would provide some useful complimentary science to what could be acquired by JEO. JGO could use its Visual and Near-Infrared Imaging Spectrometer to monitor Io's volcanic activity at spatial scales comaprable to Galileo's during that spacecraft's primary mission. These observations would improve upon similar observations by JEO by increasing temporal coverage. JGO could also provide synergistic science by observe magnetospheric and atmospheric structures at Io while JEO is flying by the moon.

Link: Jupiter Ganymede Orbiter ESA Assessment Report [sci.esa.int]

Using Ground-penetrating Radar at Io

Yesterday we took a more detailed look at the types of observations that are being planned for the Europa/Jupiter System Mission (if it's selected as the next flagship mission). The Final Report for the Jupiter Europa Orbiter also provided us with details of the encounters planned in the current reference trajectory for the mission. One of the types of observations that I want to talk about today is sub-surface sounding using the Ice Penetrating Radar (IPR). This is a type of observation that has never been done at Io and I have become curious as to what IPR (or a similar instrument) could see if it were turned at Io.

The Ice Penetrating Radar would work in a similar fashion to the MARSIS and SHARAD instruments currently at Mars on board Mars Express and Mars Reconnaissance Orbiter, respectively. Using a pair of antennae, IPR would emit pulses of high-power radio waves at the surface of the target body. These waves would first bounce off the surface and then structures in the sub-surface which become more difficult to detect the deeper you get as the signal returned becomes fainter. Basically, when the radio waves first encounter the surface, some of the waves are bounced back to the spacecraft, while others bounce down into the sub-surface, where it will then encounter another reflecting surface. This layer (or fault plane) will then bounce radio waves upward back toward the spacecraft or further into the sub-surface. This process continues until the amount of signal from a sub-surface layer doesn't rise above the noise level or is interfered with by other signals coming back.

The IPR will have two frequency modes: a 5-MHz (60-m wavelength) deep mode and a 50-MHz (6-m wavelength) shallow mode. When JEO is orbiting Europa, the shallow mode would be used to identify near-surface pockets of water while the deep mode would be used to search for the interface between the ice crust and the liquid water ocean beneath. At Europa, the IPR is expected to be able to sense layers as deep as 3 km using the shallow mode and 30 km using the deep mode. There are trade-offs to using each mode. While the 5-MHz mode can sense much deeper into the Europan sub-surface, it has a lower vertical resolution, 100 meters. The 50-MHz mode can not penetrate as deeply, but the vertical resolution in this mode is 10x better, 10 meters. So the shallow mode would be able to over thinner layers and smaller structures than the deep mode could. So the mode used on a particular orbit of Europa would need to be chosen based on what the scientists are trying to look for: small pockets of water near the surface or a broader perspective on the thickness of the water-ice crust. IPR also has a raw data mode, which would record the high-bit rate, unprocessed data for processing on the ground (rather than in the instrument electronics). This mode would be used for high-science value targets but the JEO final report doesn't provide information on which wavelengths would be used (at the moment I presume both).

The IPR would be used during two of the Io flybys, Io-1 and Io-4 - the two low-altitude encounters currently planned. For both encounters, the raw data mode would be used for the two minutes surrounding closest approach, providing a 1000-km long swath across Io's surface. During these encounters, the Laser Altimeter would also be used to help verify the surface heights measured by IPR. Now, obviously, near-surface properties of Io and Europa's crust are quite different. Io's near-surface should consist of a mix of basaltic rock and sulfur and sulfur dioxide ices. These differences in the material properties of their lithosphere should result in differences in the depth IPR can penetrate into Io's crust compared to the values given in the Final Report for Europa orbital science. Now, the best figures I could find for radio sounding penetration depths in basalt suggests that IPR should be able to sense layers as deep as 50-wavelengths below the surface. This would translate to 300 meters for the 50-MHz mode and 3 km for the 5-MHz mode. I am not sure if the vertical resolution also scales (1/10th of the ice penetration depths). For this discussion, I will presume that it doesn't. If any of these figures seem incorrect, please let me know so I can post a correction.

Now with those depths and vertical resolutions, what kinds of structures would IPR see? Let's take a look at two potential swaths, shown at left. During the two minutes surrounding closest approach during the July 2026 Io-1 encounter (300 km at C/A), the JEO spacecraft would pass just north of an unnamed active volcano, then travel southeast across the Maui portion of the large Amirani flow field, then across an active patera thought to be the source vent for Amirani, and then over the older flows at Amirani as well as the plume deposit from the volcano. After passing over Amirani, JEO would continue to travel southeast, finally passing over the 6-km tall mountain Monan Mons. During the two minutes surrounding closest approach during the December 2026 Io-4 encounter (75 km at C/A), JEO would pass over four paterae, including two active volcanoes: Malik Patera and Altjirra Patera (the two dark patera under the flight path, left and right respectively). No topographic structures beyond these paterae are under the flight path. The flight path would also cross a couple of old flow lobes associated with Arusha Patera.

Using the 5-MHz band, assuming a penetration depth of 3 km and a vertical resolution of 100 meters, IPR could look at tectonic structures in the upper crust as well as search for shallow magma reservoirs. As far as tectonic structures go, IPR could look at the faults that underlie the mountain Monan Mons. This mountain is thought to have been uplifted by imbricate thrust faulting, and IPR could try to look for these faults to test this hypothesis. IPR could also look at the connection between tectonism and volcanism by look at how deeply paterae bounding faults penetrate. Do these faults reach as far down as the shallow magma reservoirs? It should be pointed out that most of these reservoirs are expected to be located at depths between 4 and 10 km, so they maybe too deep for IPR to detect. However, Leone et al. 2008 reported that Prometheus' shallow reservoir could have a rough as shallow as 3 km below the surface, so it might be possible for IPR to detect magma bodies below the surface of Io.

Using the 50-MHz band, assuming a penetration depth of 300 meters and a vertical resolution of 10 meters, IPR could examine near-surface layering of sulfur and sulfur dioxide with basaltic lava flows, comparing the depth of these layers with evidence for sapping. A 10-meter vertical resolution might be enough to resolve layering from individual eruptions, though it would be insufficient to resolve individual flow lobes, which would be on the order of one-meter thick. The 50-MHz band could be useful for looking at layering in the plains of Io, which would allow scientists to better understand how they've been built up over time.

As you can see, both IPR modes could be very useful for examining some important science questions for Io, particularly the origin of mountains and paterae by examining sub-surface structures hidden by the surface layer of sulfur and sulfur dioxide frosts and ices. IPR can also examine how fractured Io's crust really is. If a choice had to be made between the shallow and deep modes on each encounter (meaning the raw data mode doesn't use both bands), I think it would be better to use the deep mode during the first encounter over Amirani, due to its usefulness for exploring deep structures such as mountain-forming faults and shallow magma reservoirs. For the other encounter, both modes could be used, but I think the lack of mountains, and the use of deep mode to explore the deeper structure under Amirani, would make the shallow mode a bit more useful for exploring how the plains are built up and for looking at the shallow sub-surface of the volcanoes in this region. Regardless of which mode is used, it would be very useful if context images from the wide- or medium-angle camera were acquired during closest approach so that structures observed by IPR and the Laser altimeter can be correlated with structures on the surface.

Io Science with EJSM Part Deux

Now that the more detailed mission studies for both the Jupiter Europa Orbiter and the Jupiter Ganymede Orbiter are now online, we can delve a little deeper into the science plans for Io. For some background from the Joint Summary Reports posted last month, check out my first Io Science with EJSM post. Again, Van Kane will cover the Titan stuff from the TSSM in detail. Don't forget that the downselection meeting was today (no, I don't know who won), and an announcement should be made some time early next week.

The only comment that I have about the TSSM reports is that the ESA people should have checked with me to make sure that they had the right longitude system for that map of mine they were using. Though really they didn't have to, Kraken Mare was on that version of the ISS map [see the TSSM In-Situ Elements Assessment Report, page 71], and they still had their landing site off by 180 degrees.

The JEO Final Report is a fairly extensive document detailing the current of state of our knowledge of the Jovian system, the science objectives for the Jupiter Europa Orbiter and the Europa/Jupiter System Mission as a whole, the mission concept (including model payload, mission design, and spacecraft design using floor and baseline budgets), and planned science operations. The document itself weights in at almost 500 pages so it is a bit difficult to summarize the entire document in a single post. This document is more extensive than the EJSM Joint Summary Report discussed earlier. That's why I've chosen for this first post to focus on the Io-related science plans and mission concept.

The Final Report defines two primary science investigations for Io that would be performed by JEO: Investigate the nature and magnitude of tidal dissipation and heat loss on Io and Investigate Io's active volcanism for insight into its geological history and evolution (particularly of its silicate crust). These science objectives fit with in the mission goal of understanding Europa in the context of the Jupiter System.

To accomplish these goals, the JEO team would use most if not all of the instrument payload, which while not optimized for Io science, would go a long way to furthering our understanding of Io place in the Jupiter system and its evolution. For example, using the imaging systems, the JEO team plans to image 30% of Io with a resolution better than 1 km, which is comparable to coverage provided by Galileo and Voyager. The also plan on imaging 20% of Io at better than 200 meters/pixel (compared to 3% for Galileo), 5% at better than 50 m/pixel (compared to ~1% for Galileo) and a still to-be-determined amount at better than 10 m/pixel. 10 m/pixel imaging may be precluded by the slow reaction wheel turn time and fast speed of the two, planned close flybys of Io. In addition, the JEO team plans to acquire two Ice Penetrating RADAR swaths, 1000 km long, of Io during those two encounters. These would allow observations of sub-surface structures such as fault planes and shallow magma reservoirs. No information is provided on how deep IPR could sense in silicate rock. The Thermal Instrument will observe Io's night-side in order to better constrain Io's heat flow, which is important for understanding tidal heating on Io.

The above figure shows the ground track for the four planned Io flybys. The first, taking place shortly before JOI on December 21, 2025, would have an altitude of 1000 km and would be used to help setup the the Jupiter Orbit Insertion maneuver. As currently planned, no remote sensing observation would be acquired so as to reduce the risk to the all-important JOI, though further study if EJSM is selected would be conducted to see how much risk there actually is. The Io gravity assist would help save 200 m/s in delta-V, which amounts to a dry mass increase of 160 kg, over an earlier plan to use a Ganymede flyby before JOI to help slow the spacecraft into orbit around Jupiter. Even with the additional shielding that will be required, this still amounts to more than 100 kg in mass margin.

Between July and December 2026, three additional encounters will be performed [please note again, that details of these encounters would change, but we can still discuss them as they are described in the Final Report].

The first will take place on July 9, 2026 and will have a close approach altitude of 300 km. On approach, JEO will be able to view portions of the anti-jovian and trailing hemispheres, between 150° and 260° West longitude, at high resolution. The more northerly approach also provides an opportunity to view the north polar region at high emission angles. The Amirani plume maybe visible along the bright limb. That will be useful as the close approach point for Io-1 is directly above the Amirani plume source. If the structure of the Amirani plume is similar to Thor's (as seen by Galileo in 2001), then this encounter would allow JEO to sample the high-altitude gas plume at Amirani. The Ion and Neutral Gas Spectrometer should be able to measure the abundances of various gas components in the plume, which could provide another method for measuring the volatile abundances on Io's surface. The Ice Penetrating Radar and Laser Altimeter should be used during this encounter. The ground track for JEO during Io-1 passes over the mountains Euxine Mons and Monan Mons with an altitude of less than 1000 km, so LA should be able to provide height and structure information about the mountains, while IPR should provide quite a bit of information about near-surface faults and flexure, which can provide a lot of details about Io's crust. IPR could also help our understand of the shallow magma reservoirs and conduits for the Amirani volcano. Because the spacecraft will use reaction wheels to control pointing near close approach, the spacecrafts speed relative to Io at C/A (9 km/s), will require a kind of skeet shoot to keep the LA and IPR pointed at Io nadir and INMS pointed in the direction of motion. So these observations maybe limited to the few minutes surrounding close approach.

The second encounter (Io-2) would take place on September 3, 2026, shortly before perijove on the next orbit. This encounter is a slower, relatively high-altitude (3125 km) flyby over the south polar region of Io. This should allow high resolution (less than 50 m/pixel) NAC imaging of the south polar region. The high altitude, however, precludes Ice Penetrating RADAR observations. Inbound, JEO will observe, like the previous encounter, the terrain between 150° and 260° West longitude at low phase angles. The lower latitude of the Io-2 encounter should allow for stereo analysis of this region, which would greatly expand topographic information from the limited swaths acquired by LA and IPR. Outbound, JEO would observe the sub-jovian hemisphere in Jupiter-shine, providing an opportunity for the Thermal Instrument and the VIS-IR Spectrometer to observe Io's volcanic activity and thermal emission.

The third encounter (Io-4) would take place on December 27, 2026, two orbits after Io-2 and would include the closest approach altitude of the four encounters, only 75 km. At such a low altitude, the high priority is to sample a plume using the INMS. However, the close approach point is located between Malik and Altjirra Patarae, where no previous plume has been observed. If the IPR is pointed at nadir when JEO flies over Malik and Altjirra, the spacecraft could go a long way toward constraining the formation models of Ionian paterae by looking at the sub-surface structure of these two (fault planes and perhaps shallow magma reservoirs). Once again, inbound JEO should be able to image the portions of the anti-jovian and trailing hemispheres between 150° and 260° West longitude in sunlight. The Final Report includes a detailed observation scenario for I4, ±30 minutes of closest approach, which is graphically shown at right. IPR would observe Io ±1 minute surrounding closest approach. The most of the optical remote sensing instruments would operate prior to close approach, except TI whould would be run continuously after closest approach. The laser altimeter would acquire a ground track ±6 minutes surrounding closest approach.

In addition to these flybys, sixteen non-targeted encounters during the Jupiter tour with close approaches distances between 56,300 km and 479,000 km have been identified. Most of these encounters would provide opportunities to monitor activity on Io's anti-jovian hemisphere with resolutions ranging from 560 m/pixel to 4.8 km/pixel. One interesting opportunity comes on October 29, 2026 when JEO approaches the trailing hemisphere from a distance of 185,428 km. This should allow imaging of the Pele-Loki hemisphere at resolutions approach 1.85 km/pixel. While not as good as the 500 m/pixel imaging planned (and lost due to budget constraints) for orbit A34 in November 2002, this non-targeted flyby should provide a nice change to image Pele at reasonable emission angles, Loki, and Ra as well as terrain last best seen by Voyager 1 near the south pole. During these encounters and other opportunities during the Jupiter tour and during the fourth Europa Campaign, JEO will conduct monitoring observation, searching for surface changes, plumes (both longitudinal coverage to search for them and to create plume movies), and monitoring the evolution of Io's volcanic activity over a 2.5- to 3-year time scale.

I think I'm pretty well exhausted from typing this up. I will try to writeup more tomorrow and over the weekend. In the mean time, you all can check out the two EJSM final reports for the Jupiter Europa Orbiter and the Jupiter Ganymede Orbiter. Really, more info than my brain can handle at the moment.

Flagship Mission Downselection on February 12

The Flagship Mission Downselection Meeting will take place tomorrow, February 12. At the meeting, the Science chiefs for ESA and NASA, David Southwood and Ed Weiler, will decide between the Titan/Saturn System Mission and the Europa/Jupiter System Mission. I don't have any info on when the downselection will be publicly announced, but hopefully it will before the weekend. My current favorite is the Europa mission because of the great improvement to Jupiter system science it will provide over Galileo. As to which I think will be chosen, my money at the moment is on the Europa mission due to technological readiness and the post-MSL fallout from trying to do too much without prior tech developement on a single mission with the Titan mission.

In the mean time, the more detailed reports on the NASA-provided components are now online. These documents are much longer, both weighing in at longer than 400 pages, so it will take me a bit longer to sift through and summarize here. I will discuss the Europa report, while Van Kane over at the Future Planetary Exploration blog will discuss the Titan report.

Update 02/12/2009 3:31 AM: ustrax on UMSF.com posted an email from Athena Coustenis stating that the downselection announcement maybe made next week.

Random Thoughts from the Aether

Here is a quick round-up of random items from the web that you all might find interesting:

• Van Kane has published on his blog, Future Planetary Exploration, his thoughts on the Outer Planet Flagship mission proposals. Like, it looks like he would fine with either one being selected and shares some of my opinions. For example, one of the reasons I (barely) prefer the Europa Jupiter System Mission is that it seems to do a lot more broad science of the entire Jupiter system, including Europa, whereas the Titan mission focuses primarily on Titan and Enceladus. The Titan mission though has some amazing plans, such as the hot-air balloon and the boat.
• Yesterday's 365 Days of Astronomy Podcast has a nice overview of Jupiter's Great Red Spot.
• The Detailed mission studies for the two flagship mission proposals have not been released yet, so stop asking me.
• There are a few great videos of the annular eclipse the other day. This one is my favorite.
  

Nature Sides with Titan Mission and Finally, Which Mission Does Jason Support?

As I mentioned in the last post, Nature has a news article by Eric Hand on the run-up to the downselection of the destination of the next Outer Planets Flagship Mission. The article provides quotes from the the study teams on the strengths of both mission. Bob Pappalardo points out that the Europan mission design and the technology needed for it have almost a decade of heritage after at least five mission studies. Quoteth Pappalardo, "Are you going to pick the brightly colored horse, or are you going to ask, 'Is that horse ready to run?'" Ralph Lorenz, a member of the Titan study team, disagrees and states that, "With its atmosphere, its hydrological cycle and even its potential for cryovolcanism, Titan would mobilize a much wider scientific community."

Nature also has a short editorial covering more of the shortfalls of both mission concepts and finally comes out in favor of one of the missions. Nature cites the lengthy lifecycle of these concepts (if selected, TSSM, from mission start to the end of that mission, will cover half my life to that point) as a major factor in deciding which mission to put its hat in with. While TSSM takes longer to reach its target, the implied need for a follow-on lander for Europa is seen as a problem for that mission concept. Nature also agreed with some of my criticisms, that the orbital mission doesn't really address the habitability issue as much as the Summary Report would make you think it does. Again, that issue would require a lander (and perhaps a submarine) to more fully answer. According to Nature, the Titan mission is more self-contained as it goes further towards answer the important scientific questions at Titan without necessarily requiring an immediate follow-up mission. So Nature sides with the Titan mission.

Okay, so which mission do I support? Well, let me first say, that to be quite honest, I think I will be happy either way. EJSM would examine my favorite world in the Solar System fairly extensively, even if Io isn't the primary target. It would serve as a fine contingency plan in case the Io Volcano Observer is not selected as a Discovery mission. TSSM would more extensively study my second favorite celestial body, Titan. I have friends and colleagues I admire greatly on both study teams. On the basis purely of its study of Io alone, I would favor EJSM being selected. I also feel that EJSM's science would be far less impacted if the mission became NASA-only (because ESA decided not to go with JGO as their Cosmic Visions mission, for example) than TSSM would.

Van Kane has a nice post on his blog on a thought experiment on the potential options for the losing side. He states that because of that analysis, he feels that selecting Titan as the target for the next flagship mission as Europa could be studied reasonably with a New Frontiers mission budget, whereas it would be impossible for a Titan mission to do the same (in his experiment, he presumed, if Europa was selected and Titan lost, that NASA and ESA could pool their funds from a New Frontiers AO and from the funds gained by ESA cancelling JGO, the latter not being a real option).