2015 Io Volcano Observer Proposal

The deadline for NASA's Discovery proposals was this week. 28 proposals were submitted with targets ranging from Phobos and Deimos, to Venus, to asteroids like metallic 16 Psyche, and even Enceladus.  Of course, the one that Ionians will be pulling for is the Io Volcano Observer (IVO), proposed by a team led by the University of Arizona's Alfred McEwen and managed by John Hopkins' Applied Physics Lab, which is making its second go around after also being submitted for the 2010 Discovery Announcement of Opportunity (AO).  The Martian lander, InSight, was ultimately chosen after that AO over a great set of proposed missions, which included a boat that would've sailed around Titan's great Kraken Mare.

IVO, if selected this time around, would launch in late May 2021 with an arrival at Jupiter in February 2026 after a 510 km altitude flyby of Io.  IVO would remain in an elliptical, inclined orbit around Jupiter, flying by Io eight more times during the nominal mission between August 2026 and late December 2027.  An extended mission with nearly year-long orbits is possible, providing high-resolution, imaging coverage of Io's leading hemisphere in daylight as well as collaboration with the JUICE spacecraft.  Unlike the 2010 proposal, this year's would make use of advanced, roll-out solar panels to power the probe and its five instruments, instead of the Advanced Sterling Radioisotope Generators that are unavailable to proposal teams this time around.  These instruments include: two cameras, one narrow-angle and the other wide-angle (NAC and WAC); a Thermal Mapper (TMAP); Dual Fluxgate Magnetometers (DMAG); and a suite of particle instruments (PEPI), which includes an ion and neutral mass spectrometer (INMS) and a Plasma Ion Analyzer (PIA). There is also the potential for an add-on, student collaboration instrument, a wide-angle, near-infrared camera named HOTMAP.  While the WAC, PEPI, and HOTMAP will be bolted to the spacecraft, the NAC and TMAP will be on a ± 90° pivot, allowing for off-nadir pointing of those instruments without turning the entire spacecraft.

The mission's main goals include mapping Io's active volcanism on a more global scale than Galileo and Voyager were able to obtain, measuring Io's induced magnetic field at different points in its orbit around Jupiter to provide a better estimate for the thickness, distribution, and melt percentage of its magma ocean, mapping Io's topography including its numerous mountains, and measuring the composition of the volcanic gases that are released from Io's interior.  During two of its flybys (I0 and I2), IVO will acquire gravity science using 2-Way Doppler tracking, which combined with the gravity data acquired during a few of Galileo's encounters with Io, will constrain our knowledge of mantle rigidity.  The mission will also act as a technology demonstration for Deep Space Optical Communications, which could substantial increase the data return of future missions.

On each orbit, IVO will spend a week acquiring images of Io, allowing it to map Io so changes at its many volcanoes can be observed and to monitor hot spots and auroral emissions during four different eclipses.  IVO would also use this time to help look for Europa's elusive plumes in support of Europa Clipper, which should arrive at Jupiter shortly after IVO.  During the 24 hours around closest approach, while IVO approaches and departs from Io over its polar regions, IVO will acquire several NAC mosaics of Io along with TMAP images to map heat flow and monitor volcanism.  The NAC will also be used to acquire movies of active plumes like Pele and Marduk.  Finally, right at closest approach, the spacecraft will acquire WAC, NAC, TMAP, and maybe HOTMAP imaging swaths along with INMS mass spectra and DMAG/PIA measurements as IVO sweeps north across Io.  At least 20 Gb of data (100x the Io data returned by Galileo) would be acquired during each encounter and will be played back during the apojove part of each orbit (distant monitoring observations will also be acquired to help watch for new major eruptions).

More information about this exciting mission can be found in an abstract submitted to next month's Lunar and Planetary Sciences Conference.  A fact sheet with even more details about Io Volcano Observer is also available.  NASA expects to select three (or so) finalists for Phase A studies in September with a final selection from those sometime next year.

Link: The Io Volcano Observer (IVO) for Discovery 2015 [www.hou.usra.edu]
Link: Io Volcano Observer Public Fact Sheet [pirlwww.lpl.arizona.edu]

The University of Arizona Goes to Mars...Again

I don't usually talk about Mars, but I think for this occasion I think we can excuse it.  It is a big week here at the Lunar and Planetary Laboratory (I would literally mean "here" if it weren't for the stupid Tucson transit strike).  My boss, Alfred McEwen, has been selected to be the principal investigator of the High-resolution Stereo Color Imager, or HiSCI camera on the joint NASA-ESA Mars Trace Gas Orbiter mission.  This will be his second camera that will make it to Mars, after the highly successful HiRISE.  HiSCI will beam back images with a resolution of 2 meters per pixel.  While this is not as crisp as the HiRISE camera, HiSCI will allow the team to image a wider swath of the Martian surface.  Not only that, but the entire swath will be in color, rather than a narrow band at the center of the HiRISE swaths currently. The four colors to be used by the camera will help scientists distinguish various surface components such as water ice and dust.

Another exciting feature of the camera is its Yaw Rotation Drive.  This drive will allow the camera to scan across a target before it passes over it, then rotate so it can scan the target again when the spacecraft is directly over the surface feature.  This allows the camera to obtain near-simultaneous 3D stereo coverage, rather than using two images that are taken months apart, as is currently done with other Mars cameras, like HiRISE or CTX, or with Io stereo images like this one of Zal.  This will mean that every target HiSCI images should have stereo, allowing detailed digital terrain models to be constructed for each imaging target.

This new camera will part of the payload for the Mars Trace Gas Orbiter, a joint NASA-ESA project that should launch in January 2016.  The main goal of the mission to measure the concentration, both in general and locally, of various trace gases in the Martian atmosphere, such as methane.  Much as the sub-millimeter observations of Io's atmosphere provided insights into how sulfur dioxide, sulfur monoxide, and sodium chloride got into that moon's atmosphere, this mission is focused on discovering how these trace gases get into Mars' atmosphere, be it through outgassing, photolysis, or most intriguingly, through biology.  HiSCI will be used to image possible sources regions for these gases, to better understand their geologic context.

Van Kane has an article up on his blog that describes the Trace Gas Orbiter and the other instruments selected in more detai.

So we (and by we, I mean those at PIRL who do work on HiRISE, unlike myself) are off to Mars again.  Congratulations are in order for the HiSCI team for their selection to the payload of NASA's next Mars mission after MAVEN.  I hope MRO and the HiRISE camera will still be functioning for you guys to to joint observations.  As for myself, I will still be toiling away in the Saturn system, hoping lightning will strike a third time.

Link: UA-Operated Stereo Camera Selected for Mars Mission [uanews.org]

LPSC 2010: Science Rationale for the Io Volcano Observer

For the last couple of weeks, we have been examining the Io-abstracts submitted for next month's Lunar and Planetary Science Conference.  Today we take a look at a paper submitted by Alfred McEwen and a host of co-authors from the IVO team titled, "Science Rationale for an Io Volcano Observer (IVO) Mission." For this paper, McEwen discusses the technology and science goals and objectives for the proposed Io Discovery mission.  McEwen also touches on how IVO could expand on our knowledge of Io beyond what Galileo obtained in the late 1990s and early 2000s and what the Jupiter Europa Orbiter (JEO) will get in the late 2020s.  This research will be presented as a poster at the Mission Plans and Concepts session on Tuesday, March 2.

We've discussed this proposed mission a number of times in the past. The Io Volcano Observer mission concept was first developed as part of NASA's Discovery & Scout Mission Capability Extension (DSMCE) program.  In this study, NASA hoped to get better grasp on what could be done within the Discovery/Mars Scout program cost cap if the missions were provided two, government-provided radioisotope power sources.  NASA's goal is to test the new Advanced Stirling Radioisotope Generator (ASRG) power source on one of these low-cost missions.  The ASRGs are a much more efficient power source than current RTGs, making them a smarter choice given the limited amount of plutonium available going forward.  The Io Volcano Observer (IVO) was one of nine mission concepts that were selected for further study for the DSMCE program; that study was completed back in February 2009.

For this poster, McEwen will focus on the science objectives and goals for an IVO mission, now a possible proposal for the next Discovery AO.  Some of these goals were discussed here back in September:

1. A1 - Understanding Io's current active volcanism by understanding how its active lavas and plumes are emplaced and generated.  The team plans to acquired repeated imagery of the same volcanic sites at global scales and at high-resolution (< 10 meters per pixel) in order to monitor changes at these volcanoes.  They also plan to take movies of dynamic phenomena like plumes as well as make in situ mass spectra of plume material and Io's atmosphere.
2. A2 - Understand Io's internal structure and tidal heating mechanisms.  The IVO team will use electromagnetic sounding of Io's induced magnetic field and lava temperature measurements to measure the amount of partial melting in Io's asthenosphere.  Thermal mapping in the mid-infrared (~15-20 microns) will allow the group to map Io's heat flow.  The distribution of thermal sources on Io could help distinguish the region of tidal heating in Io's mantle, whether it is in the asthenosphere or in the deep mantle close to the core.
3. B1 - Investigate the processes that form Io’s mountains and paterae and the implications for tectonics under high-heat-flow conditions that may have existed early in the history of other planets.  This will be accomplished through high resolution stereo mapping of large portions of Io's surface, with particular emphasis on areas where we already have at least medium resolution imagery, in order to look for topographic changes on a time-scale of decades (42 years between Voyager 1 and the arrival of IVO in 2021).
4. B2 - Understand how Io affects the Jupiter system.  They plan to accomplish this through in situ measurements of the composition of Ionian volcanic products, Io's atmosphere, and the plasma and neutrals in near-Io space. They also plan to study how Ionian material is lost to Jupiter's magnetosphere.  Finally, they will remotely monitor Io's sulfur dioxide atmosphere and Na-D and OI emissions.
5. B3 - Search for evidence for activity in Io's core and deep mantle by looking for an internal magnetic field in addition to the induced field discovered last year.  Resolving the conundrum of why Io can be so active and not have an intrinsic field might help us better understand how planetary magnetosphere are created.  They also plan to investigate the neutral and plasma densities and energy flows in the Io plasma torus, plus their variations over time, and characterize the ionic radiation belts in the vicinity of Io and their influence on the surface.

In addition to these science goals, a major technology goal for this mission is to study the effectiveness of the new ASRGs. One way to accomplish this is to extend the life of the mission past its primary mission of 7-8 years (including cruise to Jupiter and Io).  They could either expand IVO's orbital period to 1 year to test the ASRGs for their entire nominal lifetimes (~14 years), or they could tighten the orbits to test how well the ASRGs handle the Jovian radiation environment.  ASRGs are needed for an Io mission as the rapid flybys require fast turn times, which a non-gimbaled solar panel wouldn't support and a gimbaled solar panel may not be stable enough and too expensive for a Discovery-class mission.  The inclined orbits of IVO would result in low doses per flyby (10 krads compared to 85 krads for the average JEO flyby), so that actually wouldn't be the limiting factor for a solar-paneled Io mission, the high turn rates and high data rates during the encounters would be.

Finally, the IVO team compare the possible science generated by the Io Volcano Observer and other missions to Io: Galileo and the Europa/Jupiter System Mission.  Galileo's instruments were designed before the discovery of volcanism on Io so the camera and near-infrared spectrometer were not optimized to take advantage of this discovery, and the limited downlink bandwidth brought on by the high-gain antenna failure didn't help.  Compared to the Jupiter Europa Orbiter, IVO would fly over Io's polar regions, mapping the heat flow in those areas and performing sounding of Io's induced magnetic field.  The instruments can also be designed to specifically perform measurements needed for Io that might not be possible with those on the Jupiter Europa Orbiter, such as the near-simultaneous color imaging needed for color measurements.  JEO would accomplish some Io science that would be complementary to that of IVO, such as ground-penetrating radar and laser altimetry.  One interesting possibility is a simultaneous close-up observation with both IVO and JEO.  If IVO's mission at Jupiter and Io is extended with year-long orbits, its extended mission could overlap with the Europa/Jupiter System Mission.

Link: Science Rationale for an Io Volcano Observer (IVO) Mission [www.lpi.usra.edu]

Io Presentations at EPSC

While normally I remember to cover the big four conferences for planetary science each year (LPSC in March, AGU in May and December, and DPS in the fall), I often forget about the main European planetary science conference, the European Planetary Science Congress or EPSC.  Io science tends to be dominated by American institutions like the University of Arizona, the Jet Propulsion Laboratory, and Arizona State University, so a European conference would be expected to have less Io coverage than those held in the US.  However, this year, three talks and one poster were presented last week in Potsdam, Germany.  Let's take a look at the abstract for these four presentations:

• The last talk in the Satellite Atmospheres session this past Thursday, September 17, was titled, "First detection of Io's atmosphere at 4.0 micron" and was presented by Emmanuel Lellouch et al. Lellouch and his colleagues observed Io in the near-infrared using the CRIRES spectrometer at the Very Large Telescope in Chile in July 2008.  These measurements allowed the authors to observe an absorption band of sulfur dioxide gas at 4.0 μm.  With the adaptive optics system at VLT, they were also able to spatial resolve variations in the absorption band, looking for differences in atmospheric column density between the polar region and the equator.  Lellouch et al. believe that these observation open up a new avenue for monitoring Io's dynamic atmosphere.
• The Satellite Surfaces and Interiors oral session this past Wednesday, September 16 hosted two Io talks.  The first was titled, "Volcanism on Io: New Insights from Global Geologic Mapping" and was presented by David Williams et al.  This talk and abstract provide an update to the Io geologic mapping project, a subject Williams presented at this year's Lunar and Planetary Sciences Conference, which I discussed in greater depth earlier this year.  This geologic map displays the distribution of various morphologic and color units across Io's surface.  Using software such as ArcGIS™ will allow researchers to use the map to conduct various lines of research, including comparing the areas of various mountain units with their heights, looking at the areal extent of the various plains units, and seeing how ongoing volcanism change these areal extent of the different lava flow units.  The authors also plan to assess the distribution of different flow units to assess regional variations in the style of volcanism (sulfur versus silicate volcanism, for example) and compare these units to observed volcanic hotspots to look for correlations between eruption style and unit types.  The Io Geologic map was completed in February 2009 and has been submitted to the USGS for peer review.  A similar global geologic map of Ganymede was also presented at the conference, which has garnered some press coverage (but not Io's, bah I say, BAH!) .
• The other Io talk at the Surfaces session was titled, "Continued Observations of Io's Volcanic Activity" and was presented by Imke de Pater et al.  In this abstract, de Pater briefly presents new results from observations of Io in the near-infrared using the adaptive optics system at Keck in Hawaii.  These results include new observations of volcanic hot spots on Io as well as the distribution of sulfur dioxide frost across Io's surface.  While the abstract left out specifics, the authors spent more time advocating for additional telescopic observations of Io.  Regular observation runs were conducted during the Galileo mission and the New Horizons flyby in 2007, but outside of that flyby, Io monitoring has been sparse the last few years.  Regular monitoring is important for understanding Io's heat flow and its active volcanism. de Pater et al. also advocate for the inclusion of narrow angle cameras on board Jupiter-bound missions, particularly EJSM, to provide for monitoring of Io and other satellites in the system.
• Finally, Ashley Davies, Laszlo Keszthelyi, and Alfred McEwen presented a poster titled, "Determining Io Lava Eruption Temperature: Strategies for a New Mission to the Solar System's Most Dynamic Satellite."  These authors presented a similar poster at LPSC earlier this year, which was discussed here a bit more extensively.  This abstract discusses how the desire to measure the temperature of Ionian lava using near-infrared camera observations of lava fountains and skylights (holes in the roofs of lava tubes).  The authors explain that near-simultaneous, high-resolution color imaging during Io flybys by either a dedicated Io mission (such as the Io Volcano Observer) or by another Jupiter system mission (like EJSM) would be necessary for determining these lava temperatures without the issues from short-term variability (on the order of a few seconds) of lava fountains.  The authors also state that these observations would need to be preformed over Io's night-side to avoid contamination from sunlight.

With EPSC now passed and DPS abstracts online for that meeting in two weeks, we now have to wait for AGU abstract to be posted online.  The Fall AGU meeting is scheduled for December 14-18 and abstracts for this meeting are usually posted online in mid- to late-October.  At last year's fall meeting, five Io-related talks and posters were presented, so we will see what this year brings.

Link: European Planetary Science Congress [meetings.copernicus.org]

Io Volcano Observer at LPSC

The Lunar and Planetary Science Conference will see two Io Volcano Observer posters. The first, by Alfred McEwen et al., is titled "Io Volcano Observer (IVO)". This poster will provide an overview of the mission concept, with the abstract providing quite a few details of the planned payload. The second, by Keszthelyi et al, is titled "Optimal Wavelengths for Studying Thermal Emission from Active Volcanoes on Io". This poster will look at some of the work that has gone into filter selection and instrument design for IVO's radiation-hard camera (RCam) and Thermal Mapper (ThM).

Much of the information in McEwen's abstract was previously reported on in my post, The Uber Io Volcano Observer Post, so I don't think I need to completely repeat myself. The abstract does include a clearer description of the imaging system to be used on IVO, RCam. The camera would use a 2000x2000 CMOS detector. The half of the detector will allow RCam to be used as a clear-filter framing camera, for taking opnav,clear filter global images, and plume movies. The other half "will be covered by up to 15 spectral filters from 200-1000 nm, each covering ~64 lines for digital Time-Delay Integration (dTDI)." For 256 lines, the instrument will have 16 sets of 4 filters, with each filter using 4 lines. The four filters McEwen's suggests using are 400-600 nm (blue-green), 600-800 nm (red), >800 nm (IR1), and >950 nm (IR2). This would allow RCam to take near-simultaneous color images that will be necessary for measuring the hottest lava temperatures as they can change over times scales of less than a second. Other filters that RCam could use include UV bandpasses (for atmospheric processes and for looking at SO2 frost), other narrow filters for looking at atmospheric composition (Na, O), mineralogy bandpasses from 800-1000 nm, and methane bands (for looking at Jupiter's atmosphere).

The second abstract by Keszthelyi et al. takes a look at the best filters to use on RCam and Thermal Mapper for measuring lava temperatures. Different bandpasses would work best for measuring lavas of different ages. For example, RCam would be used to look at lava less than a second after they emerge from the surface (such as at a lava fountain) as well as magma in lava tubes made visible through skylights. This would be supported by the two near-infrared bandpasses on RCam. Ratioing pixel values between the two would allow scientists to calculate eruption temperatures between 1200 and 1800 °C. The digital Time-Delay Integration system used by RCam would also support the need for less than 0.1 seconds between acquisition of the different color filter data.

The Thermal Mapper will use up to 10 bands in the infrared portion of the spectrum to examine Io's surface composition, thermal inertia, and thermal emission. Some of the bands that will be included would be selected based on the type of volcanic process mission scientists wish to examine. These processes occur at different time scales, which based on the cooling rate of lava on Io, can be related to different peak temperatures. The wavelengths picked (2, 3, 4, 6, and 8 microns) were chosen because they cover peak emission wavelengths for each of the time scales the scientists want to look at (processes that occur over a period of seconds, minutes, days, and months). Other bands the scientists would hope to include are 15 and 20 microns that would be used to search for SO2 at its triple point as well as to look at global heatflow. Additional bands could be included to search for the Christiansen Feature between 7.5 and 9.5 microns, which would provide additional information on the mineralogy of Io's lavas. The Christiansen Feature increases in wavelength with decreasing SiO2 content. So the CF for minerals typical of felsic lavas like rhyolite would be closer to 7.5-8 microns, while the CF for minerals typical of mafic lavas, the dominent type on Io,would be closer to 8.5-9.5 microns.

Way cool stuff!

Link: Optimal Wavelengths for Studying Thermal Emission from Active Volcanoes on Io [www.lpi.usra.edu]

The Uber Io Volcano Observer Post

My boss Dr. Alfred McEwen has given me permission to post the presentation on the Io Volcano Observer (IVO) mission concept he gave a few weeks ago at the Io Workshop in Berkeley, California. You can find the presentation here. The presentation covers mission design, mission goals, baseline and optional payloads, and risk assessment.

Mission Design

The current mission design calls for a January 2015 launch (with a window from late 2014 to early 2015). IVO would be launched into a Venus-Earth-Earth gravity assist trajectory, similar to the interplanetary path taken by Galileo between 1989 and 1995. Calibration for IVO's various instruments would be performed during one of the Earth encounters, though McEwen does note that an asteroid encounter during one of the apohelions could be used as a dress rehersal for the Io flybys.

After a six-year cruise, IVO would enter orbit around Jupiter in 2021. Prior to Jupiter orbit insertion, IVO would perform its first flyby of Io. While other information I have found suggested that no science would be acquired during this first encounter, McEwen presentation points out that the reason for performing this encounter is to acquire unique equatorial science since the encounter doesn't actually reduce the delta-V, like the inital Io flyby did for Galileo. IVO would be inserted into an inclined, 200-day-long initial orbit following JOI.

During IVO's orbital tour, planned to last at least 1.5 years, the spacecraft would flyby Io at least six more times, with the goal of having more than ten flybys with the help of an extended mission. With the various sources I have, I am not certain if they plan to have six flybys during the primary mission with at least four more during an extended mission, or if the six-flyby number is only a baseline for mission success. The trajectory design calls for the Io flybys to also be used to "pump down" the spacecraft's apojove, eventually bringing IVO's orbital period down to 30 days. The first few flybys of Io would be further out, with altitudes between 500-1000 km, until estimates of Io's position are refined. Later encounters can then be brought down to altitudes approaching 100 km, supporting magnetometer and mass spectrometer science. Like Galileo, data would mostly be taken during the few days surrounding perijove and would be transmitted to Earth near apojove, though the much greater bandwidth with IVO would support more apojove science, such as imaging of Jupiter and eclipse observations of Io and Europa. Also, thanks to IVO's increased bandwidth, up to 20 Gb of data would be returned after every flyby, much greater than Galileo's entire Ionian dataset. I can't recall, but that maybe more data than Galileo returned during its entire Jovian tour.

For planetary protection purposes (God forbid we contaminate poor Amalthea), the spacecraft would be impacted with Io at the end of its life. However, several end of mission scenarios have been developed, including one that would put IVO into very large orbits, with periods up to one-year in length, in order to monitor Io for up to a decade and to perform a lifespan test for the Advanced Stirling Radioisotope Generator (ASRG), the next-generation power source to be used by IVO. In another scenario, IVO's perijove would be raised to pull it out of the worst of Jupiter's radiation belts, again to extend the spacecraft's life, though there maybe issues with the requirement to dump IVO on Io at the end of the mission.

Mission Goals

Io Volcano Observer, being half a science mission and half a engineering test, has a very focused set of mission goals. As you can see in the slide at right, the primary objective of this study is to see if an Io mission can be accomplished with a Discovery budget, assuming NASA furnishes the ASRG and NEPA.

The baseline mission was designed as simply as possible while still accomplishing a focused set of science goals. From the presentation, these include:

1. Understanding active Ionian volcanic processes
2. Understanding the process of tidal heating
3. Understanding loss of material from Io and following that material to the magnetosphere, plasma torus, and neutral clouds

IVO's planners also want to test out the ASRG for as long as possible, thus the desire to extend the lifespan of IVO as long as possible before crashing it into Io. In additions, measurements of the radiation environment will help planners of future missions to the Jovian system.

There are also secondary goals to study the rest of Jovian system. Most of these observations would be acquired near apojove. These include: monitoring of Jovian clouds systems near the poles (complementing data from Juno), distant observations of the Galilean satellites including Europa's atmosphere, close-up observations of Jupiter's inner moons near perijove, and observations of Jupiter's rings and the Io Plasma Torus. Due to data volume restrictions on the later, shorter orbits, many of these observations would be acquired during the initial, 200-day orbit, when data volume would be more plentiful.

Payload

At the Io workshop, McEwen presented details on the planned baseline payload as well as other instruments that could be used on IVO. With this payload, McEwen and his team hope to accomplish the science goals discussed above.

The baseline payload for IVO includes the following instruments: a narrow-angle camera with an angular resolution similar to Galileo, a thermal mapper similar to THEMIS on Mars Odyssey, an Ion and Neutral Mass Spectrometer, and magnetometers. Other potential instruments outlined by McEwen include a wide-angle camera, a near-IR spectrometer, and an EUV/FUV spectrometer.

The narrow-angle camera, as outlined by McEwen, would provide medium-resolution surface monitoring and high-resolution surface imaging during flybys, while keeping noise to a minimum. Unlike most spacecraft imagers in use, the camera would use a CMOS focal-plane system with both framing and pushbroom modes. The fast readout times for the CMOS system would help keep radiation noise down by reducing the amount of time between the image exposure and its storage in memory. The CMOS detector would be split up so that the bottom half of the detector (1000 lines by 2000 columns), would be used for clear filter, framing-mode imaging, similar to Cassini's ISS. Up to half of the detector would be used for color filter, pushbroom imaging, similar to the Mars Reconnaisance Orbiter's HiRISE camera. This upper section would consist of up to 15 color filter strips of 64 lines each. These strips would use digital Time-delay Integration to produce nearly simultaneous color imaging (necessary for lava temperature measurements), super-resolution, and faint-target imaging. At minimum, McEwen's group would like to include broadband UV, blue-green, red, and near-IR dTDI lines, though other filters could be included, mostly narrowband filters designed for spectroscopy.

IVO's thermal mapper would be designed much like Mars Odyssey's THEMIS instrument. The instrument would include at least three bandpasses between 2 and 20 microns and would have a resolution about 12.5x coarser than the NAC (assuming new detectors are used, compared to THEMIS). With Thermal Mapper, IVO planners hope to map and monitor Io's thermal emission, perform thermal emission spectroscopy, and analyze Io's polar thermal emission and compare it with results from Galileo at low latitudes. For a baseline mission, the expected bandpasses would be at 2, 5, and 20 microns, though more bandpasses maybe possible. Some that interest IVO planners occur between 7 and 9.5 microns, wavelengths diagnostic for silicate mineralogy.

The Ion and Neutral Mass Spectromter (NMS) was covered recently in a blog post, so check that out for details of that instrument. IVO planners seem confident that they can detect most of the expected species in Io's atmosphere (like SO₂, SO, O, and NaCl) thanks to its high signal-to-noise ratio and 1-300 amu mass range.

The final pieces of the baseline payload are a pair of fluxgate magnetometers. These very small magnetometers would be attached to 1-meter long brackets bolted to the spacecraft. These magnetometers would be similar in design to those carried on recent ESA planetary missions. Now whether they would actually find a magnetic field at Io...

These instruments would be bolted to the top deck of the spacecraft, below the High-gain antenna. This would force decisions between having a gravity pass and a remote-sensing pass, much like Cassini. Much of the electronics for these instruments would be stored below this top deck, in a radiation-shielded "vault", in hopes to reduce the chances for radiation affecting measurements.

Risks

A major limiting factor for the lifespan of IVO is the high charged particle environment near Io. Even with the high-inclination orbits, IVO planners expect betwen 115 and 230 krads, though the spacecraft electronics may have a much reduced exposure during the primary mission.

Another issue is the current projected price tag. A JPL Team X assessment in November came up with a cost $471 million. I'm not sure if that is for the baseline mission, but at least $21 million will need to be trimmed from the estimated budget to get IVO within the Discovery costcap.

Conclusion

This presentation lays out a pretty compelling case for a cost-effective mission to Io. As of earlier this month, IVO planners were preparing to finish their final report for the DSMCE program and were looking forward to submitting this proposal for the next Discovery Announcement of Opportunity coming (hopefully) sometime around mid-year.

Link: Io Volcano Observer (IVO) [pirlwww.lpl.arizona.edu]

Io Volcano Observer at LPLC

Yesterday was the second and final day of the Lunar and Planetary Laboratory Conference in Tucson, Arizona. This is a small conference where researchers at the University of Arizona's Lunar and Planetary Laboratory can share their current work with their colleagues here. Many of the talk in the morning where dedicated to dynamics and space physics. I am amazed I stayed awake...

The afternoon sessions included Titan and other satellites in the Solar System. I gave a talk on Cassini images of Titan, particularly those of Titan's polar regions. Alfred McEwen, my advisor, gave a talk on the Io Volcano Observer (IVO, pronounced eye-voh), a mission concept in the Discovery & Scout Mission Capability Expansion (DSCME) program. I have reported on this concept study previously and on the abstract McEwen submitted to the conference.

The talk provided a few new details on this mission concept. The IVO team is aiming for a 2013 launch on an Atlas V with a back-up launch date in 2014. The spacecraft would be launched into a Venus-Earth gravity assist trajectory with an arrival at Jupiter in the 2019 timeframe. Once at Jupiter, IVO would flyby Io shortly before Jupiter orbit insertion, which would lower JOI delta-V and provide an insurance flyby in case any issues occur during the JOI burn. Once at Jupiter, IVO would be injected into a 200-day orbit around Jupiter with a 45 degree inclination.

Over the course of the 1-2 year mission, IVO would use 5-10 Io flybys to bring its orbital period down to 30 days. Each flyby would have a close-approach distance between 500 and 1000 km with 100 km flybys possible later in the mission. The high-inclination orbit would provide much needed polar coverage, which would be complementary to observations acquired by Galileo and the Europa orbiter mission. Flybys would occur at similar solar longitudes on Io to reduce the variables when comparing images between flybys.

The base payload for IVO includes a narrow-angle camera, a Thermal Imager, a Neutral Mass Spectrometer, and a Radiation detector for a total payload weight of 34 kg (44 kg with 30% margin). The nominal narrow angle camera planned would weigh 15 kg and would have a resolution of 10 microradians per pixel (the same as Galileo SSI). The goal for this camera is to observe Io's ever-changing surface by observing the same volcanic features during each flyby. The camera would also be used to measure Io's limb topography, which would help constrain Io's tidal bulge and thus provide constraints on Io's current tidal heating. The camera will make use of active pixel sensors, which have increased radiation hardness compared to traditional CCDs. These sensors will also allow the IVO team to acquire simultaneous multi-spectral imaging. This would make acquiring color mosaics a much simpler task as well as help support lava temperature measurements, since lava fountains can change on the order of seconds.

The Thermal Imager would be similar to the THEMIS instrument on the Mars Odyssey spacecraft. The IVO team is looking for an instrument that would acquire near- to mid-IR imaging at 3, 8, and 20 microns, to measure Io's heat flow. Assuming something akin to THEMIS is used (which is possible considering that the PI for THEMIS, Phil Christensen, is on the IVO team), the Thermal Imager would have a 4.6 deg. FOV with 250 microradians/pixel resolution (effectively 1 km/pixel per 4000 km).

Unfortunately, Alfred was nearing his alloted time by the time he finished discussing the Thermal Imager so he didn't spend time covering NMS, UVS, and the Radiation Detector. He pointed out that the "Powerpoint" mission might have a chance in Hell of flying, considering that Io is a world of fire and brimstone, there is a team member named Dante, and that Alfred will be 66 years old when IVO arrives at Jupiter (assuming that IVO flies on the back-up 2014 VEEGA trajectory).

More Details on Io Volcano Observer

As mentioned last month, NASA has commissioned several concept studies for Discovery-class mission that make use of the new Advanced Stirling Radioisotope Generator (ASRG) power source, a more efficient RTG that makes use of plutonium for power. One of these concepts is the Io Volcano Observer (IVO), a mission to study Io's volcanic activity.

The leader of the study, Alfred McEwen, submitted an abstract on the mission concept to the Lunar and Planetary Laboratory Conference (LPLC) to be held next week in Tucson. I will be there giving a talk on the state of Cassini Imaging, particularly imaging of Titan. The abstract makes public a few more details on the study. The IVO team envision a small spacecraft that orbits Jupiter in a highly inclined orbit, encountering Io at every periapse. The high-inclination orbit helps to reduce IVO's radiation exposure during periapse. Each orbit would last between 30 and 200 days, though shorter orbit would provide better distant monitoring.

Due to the low-cost of the mission, the payload has to be kept simplistic. The team has currently include a baseline payload of a narrow-angle camera (with some color imaging capability), a thermal imager (capable of mapping Io's thermal emission at 3, 8, and 15 microns, and at some silicate absorption bands), a Neutral Mass Spectrometer, and a Radiation detector. Other potential instruments include a Wide-angle camera, an ultra-stable oscillator (used for gravity measurements), a near-infrared spectrometer (I guess a toss-up between this and the thermal mapper), an ultraviolet spectrometer, and a magnetometer.

The team has also outlined the scientific goals for this mission which include understanding Io's volcanic processes, composition, heat flow, and environment.

Link: Mission Concept: Io Volcano Observer (IVO) [www.lpl.arizona.edu]