New Posts Will Resume This Weekend

I'm in the midst of attending a couple of scientific conferences, and so will begin posting again this coming weekend.

New Requirement for Comments

There apparently is a cottage industry of posting spam in comments on blogs.  Most recently, a 'gg' has been posting in what appears to be identical Chinese characters.  I hope that the content is not offensive.

My policy is to allow all posts that are on topic and respectful of other's opinions.  However, I have turned on a feature that requires you to enter characters displayed to post a comment.  I dislike this feature whenever I encounter it, and I'm sorry to have to enable it here.

Please do continue to post comments!  They let me know that there are interested readers and allow me to answer questions.

Bruce Moomaw has Passed Away

I learned today that Bruce Moomaw passed away  in February. 

Bruce had a long standing interest in planetary exploration and the planning of future missions.  His many detailed analyzes of future mission planning at Space Daily reawakened my own interest.  When I began this blog, I had hoped that Bruce would be a regular contributor, and he contributed as his health permitted. 

Bruce was enthusiastic and committed to seeing planetary exploration continue.  He frequently held strong opinions on what the right course would be, and I often learned more from his defense of those explanations than I did from simply reading the factual descriptions of the options.

I never met Bruce, but I came to look forward to his articles and e-mails.  His contributions will be missed.

Bruce loved to write about planetary exploration.  I can think of no better tribute than to provide links to the major posts he contributed to this blog.  You can find many more of his articles at SpaceDaily.

SAGE New Frontiers Proposal (Enhanced)

Osiris-Rex New Frontiers Proposal

New Mars Sample Return Plan

New Mars Sample Return Mission - Part Two

First Response to a Galilean Satellite Observer

A Cheaper Way to Measure Venus Surface Composition?

Options for Exploring Venus in Smaller Chunks

Venus Flagship Proposal

EJSM Jupiter Science

Two previous blog entries (see Overview and Satellite Flyby Science) have looked at the science that the Europa Jupiter System Mission (EJSM) could perform prior to the two spacecraft entering orbit around Europa and Ganymede.  This blog entry looks at the science that could be performed by observing Jupiter itself.  The material for this discussion is drawn from the Jupiter Science and Capabilities on the Europa Jupiter Science Mission presentation made at the last OPAG meeting in February.  The presentation focuses on science that could be performed on the visible outer layers of Jupiter, including the weather layers with their swirling cloud decks.

To provide new science, the EJSM mission must build on results provided by past and planned missions.  Four spacecraft with instruments suitable for observing this world's weather have conducted studies: the two Voyager spacecraft, Cassini, and New Horizons.  All were limited by short observation times and except for Cassini possessed either 1970s technology instruments or instruments not optimized for gas giant observations.  The Galileo craft orbited Jupiter for a number of years, but it suffered from both 1970s vintage instruments and a malfunctioning antenna that severely crippled planned observations of Jupiter.  The Galileo probe did successfully enter Jupiter's atmosphere and provided irreplaceable composition measurements that, unfortunately, were not fully typical of the planet since the the probe entered a hot spot, which is the equivalent of a Jovian desert.  Key measurements of water and clouds could not be made.  In addition to these past missions, by the time EJSM arrives in the mid 2020s, the Juno orbiter will have completed its studies of the bulk composition of Jupiter and structure of the planet below the cloud tops.

The EJSM mission would bring several new capabilities to the study of Jupiter:

• Modern instruments that span the spectral range from 70 nanometers (ultraviolet) to 2 micron (mid-infrared)
• Multi-year observations with large data storage systems and high bandwidth communications systems
• Two spacecraft that can study the clouds decks at different times and at other times observe the same features to produce 3D images
• Two spacecraft that can probe the atmospheric structure by tracking each other's radio signals as they pass behind Jupiter as viewed from each other

A science working group identified three key science objectives: atmospheric dynamics and circulation, atmospheric composition and chemistry, and atmospheric vertical structure.  Some of the more detailed questions that struck me as particularly interesting (and you can read the entire list on pages 19-21 of the presentation) included:

• Investigating the dynamical of the weather layer to understand the redistribution of energy and momentum (particularly interesting on a world where a solid surface doesn't steal energy from wind systems)
• Coupling of the weather layer patterns with the deep interior
• Study localized variations in atmospheric composition
• Determine the 3D structure of Jupiter's atmosphere from deep within the clouds to the upper troposphere

The strawman payload of the NASA Jupiter Europa orbiter (JEO) would provide a range of resolutions (quoted resolutions are from 9.5 Jupiter radii):

• 7km/pixel from the narrow-angle camera
• 70km/pixel from the medium-angle camera
• 170km/pixel from the near-IR spectrometer
• 700km/pixel from the wide angle camera and UV spectrometer
• 1700km/pixel from the thermal

The planned orbits for the two craft would place perijove on the sunlit side of the planet.  These means that for the majority of each orbit, the instruments would view the night side of planet.  As a result, most of the atmospheric observations would take place in the three days centered on each perijove when the sunlit Jupiter would be visible (which represents approximately 10% of the time).  During this time, both contextual images and hundreds of narrow angle camera images would be taken to produce nearly 25GB of data per orbit.  A key strategy would be to repeatedly image the same locations on the cloud deck in multiple wavelengths to track evolution of cloud structure across the daytime and between days.

The current strawman instrument list and mission orbits are optimized for studying the Galilean moons, not the atmosphere of Jupiter.  The science working group identified a number of areas in which the mission could be enhanced:

• Optimize the spectral coverage of the instruments to observed key wavelengths to probe structure and composition
• Improve spatial resolution of the near-IR and UV spectrometers
• Add instruments specifically designed for probing Jupiter's atmosphere including a mid-to-far IR (5-500 microns) spectrometer and a sub-mm (500-1000 micron) spectrometer on the NASA spacecraft and a thermal imager on the European spacecraft
• Consider lengthening the orbital tour so that the apoapses of later orbits could lie on the daylight side of Jupiter for more observing time

Even without these enhancements, the EJSM mission would provide a major advance in our understanding of Jupiter and by extension the gas giants that have been found orbiting other stars.  Where Juno will focus on the interior of Jupiter, EJSM will focus on the top-most levels of the atmosphere.  In the words of the presentation, "Together, EJSM and Juno would provide the tools to significantly enhance our understanding of the fundamental physical processes in gas giant atmospheres... A long baseline of high resolution observations would allow us to construct a Jupiter 'climate database' to inform detailed physiochemical models of the atmosphere and the coupling processes between layers."

AVIATR poster

Mike Malaska has posted the poster used at two recent conferences for the AVIATR Titan airplane concept.  Click on the picture to go to his flickr page.

You can read an abstract on this Discovery mission proposal here. 

Discovery Program Update

A community announcement regarding the selection of the next Discovery program mission has been posted by NASA.  This next selection can target missions to any planet, moon, or small body, including Mars.  The total mission cost is capped at $425M, not including the launch vehicle and any of several government supplied technologies, including an ASRG plutonium power supply.  By providing the launch vehicle and other technologies, NASA has substantially increased the scope of missions that can be flown within this program and the range of destinations.  Click here, on the Discovery Missions link, to read about several mission concepts that have been publicly discussed.  [As a side note, the launch date limitation in 2017 might allow the proposed ARGO Neptune/Triton/Kuiper belt flyby mission to be funded within this proposal.  While the schedules apparently overlap, I don't know if the ARGO mission could be flown within a Discovery budget.  The ARGO spacecraft would be similar in scope to the proposed Discovery Io Volcano Observer, and ARGO would require a plutonium power supply.  I expect that the ARGO will see if there is a fit.]

"NASA’s Science Mission Directorate (SMD) intends to release an Announcement of Opportunity (AO) for Discovery Program missions no earlier than (NET) June 2010. The Discovery Program conducts Principal Investigator (PI)-led space science investigations in SMD’s planetary programs under a not-to-exceed cost cap. It is anticipated that approximately two to three Discovery investigations will be selected for 9-month Phase A concept studies through this AO. At the conclusion of these concept studies, it is planned that one Discovery investigation will be selected to continue into Phase B and subsequent mission phases."

The announcement goes on to list several technical and budgetary changes to the planned Announcement of Opportunity (AO) before listing the expected schedule for mission selection and flight:

Release of final AO (target)     NET June 2010
Pre-proposal conference     ~3 weeks after final AO release
Proposals due     90 days after AO release
Selection for competitive Phase A studies     March 2011 (target)
Concept study reports due     February 2012 (target)
Down-selection     July 2012 (target)
Launch readiness date     NLT December 31, 2017

You can read the entire announcement at http://discovery.larc.nasa.gov/announcements.html

Two Tidbits

Thanks to anonymous for the link to a presentation on ESA's planned MoonNEXT mission that would land a craft near the moon's south pole.  From this presentation, it's clear that the lander would be expected to survive for some time -- instruments such as a seismometer are included in the list of possible instruments.  You can look at the presentation at  http://www.lpi.usra.edu/meetings/leagilewg2008/presentations/oct30am/Carpenter4037.pdf 

or read my original discussion at http://futureplanets.blogspot.com/2010/04/europe-plans-moon-lander.html#comments

The minutes from the last MEPAG meeting have been posted.  For the most part, they summarize the presentations and the findings echo those of the presenters.  However, the minutes note the MEPAG members' concerns that the 2016 Trace Gas Orbiter and the 2018 ExoMars and MAX-C rover missions "are already struggling with tight technical and financial margins.... The 2016 Orbiter mission has an ambitious program of scientific and technical objectives within a highly constrained resource box.  There is concern that, without dedicated effort on the part of both NASA and ESA, the mission's ability to address its compelling scientific objectives will be compromised during the development phase."   You can read the entire set of minutes at http://mepag.jpl.nasa.gov/meeting/mar-10/MEPAG_Mtg-Report-March-2010.pdf

EJSM Satellite Flyby Science

Mercury as imaged from the MESSENGER spacecraft in January 2008.  2.8 km/pixel resolution at the equator.

This week's blog entry continues looking at the science the Europa Jupiter Science Mission (EJSM), which could consist of at least NASA's Jupiter Europa Orbiter and possibly ESA's Jupiter Ganymede Orbiter. (See this blog entry for the introduction to this series.)  Both missions still face a selection hurdle.  JEO must be prioritized by the Decadal Survey and JGO must win out in a selection against two astronomy missions.

Prior to entering orbit around their namesake moons, both craft would perform a number of flybys of the Galilean moons.  Messenger's flybys of Mercury and Cassini's flybys of Saturn's moons have shown what modern spacecraft with modern instruments can do from quick encounters.

JEO and JGO would bring three key assets to a tour of the Galilean moons:

• They would have working antennas to return torrents of data compared to the trickle of data from the Galileo orbiter with its crippled antenna
• They would carry instruments new to studying icy moons including laser altimeters and ice penetrating radars
• They would have modern instruments that would be three decades more advanced than the instruments carried by Galileo

Perhaps the single greatest accomplishment these craft could perform would be to extend our high resolution coverage of these moons.  This map shows the resolution of the current coverage for Ganymede following the Voyager and Galileo missions:

The next map shows the resolution of coverage that would be possible from the current, nominal JEO mission, which may well be improved as mission design progresses:

The strips of high resolution coverage would be the ground tracks beneath JEO as it makes its closest approach.  The JEO instruments would be designed to capture data as the craft orbits Europa, and this ability to acquire data rapidly apparently would be employed to provide very high resolution images beneath the ground tracks during flybys.  The cameras would also be able to acquire images at greater ranges (and lower resolutions), much as the Cassini cameras have for Saturn's moons.  Certain instruments, such as the laser altimeter and ice penetrating radar, however, would operate only during closest approach.

The following chart shows the coverage the nominal JEO mission would provide for each moon from the flybys.  IPR is the ice penetrating radar and LA is the laser altimeter.

Of the two craft, JEO would have the more capable instruments (part of what the ~$3B JEO price buys compared to the ~$1.2B JGO price).  The following two maps show image coverage of Callisto following JEO's nine and JGO's fifteen flybys of Callisto:

The flyby science campaign would provide incredible advances in our understanding of these moons.  However, it is important to place the return in perspective.  The orbital geometry of the missions mean that the high resolution coverage occurs over only a single hemisphere for each moon.  It is my understanding that with time, the orbital geometries could be changed to view the opposite hemisphere and the science analysis group as asked if this could be reasonably done.  I expect that it is a tradeoff between more science from flybys versus the risk of the craft not surviving for their prime missions in orbit about their respective moons.

Multiple flybys also aren't a substitute for studies from orbit to understand the processes that have formed moons.  An orbiter can image the entire surface in high resolution and selected portions in very high resolution.  Certain instruments crucial to understanding the structure of the surface and interior such as the laser altimeter, ice penetrating radar would gain relatively little from flybys (see how limited the ground tracks would be in the chart above), but could provide global coverage from orbit.  Should NASA and ESA decide not to fund Galilean satellite orbiters, a Cassini-like spacecraft could substantially enhance our knowledge of these moons, but future orbiters would still be needed in the future.  For comparison, imagine if instead of orbiters around Mars, we had only a dozen flybys of that world by Cassini.  We would have global maps of what was there, but likely only a limited understanding of the processes that created the surface.

It's also reasonable to speculate how the missions might change if only one of the craft eventually flies.  JGO would not be designed to handle the radiation fields inside the oribit of Ganymede, so it would be difficult for it to add significantly to our knowledge of Europa and Io.  The JEO mission, however, could be lengthened to provide additional flybys of Callisto and Ganymede to extend high resolution coverage.  In theory, additional Io flybys could also be done, but the tradeoff there would be the additional radiation exposure that each of those flybys would cause.

References:

All images except the opening Mercury image are from these two presentations made at the last OPAG meeting:

NASA-ESA Outer Planet Flagship SDT
Ron Greeley, Arizona State University
Olivier Grasset, Université de Nantes


EJSM Satellite Science
David Senske, Jet Propulsion Laboratory

Note: Jason Perry has excellent summaries of what JEO could do during its flybys of Io at 

Io Science with EJSM

Io Science with EJSM Part Deux

Io Science with the Jupiter Ganymede Orbiter

Animation of the Jupiter Europa Orbiter's Four Io Flybys

Europe Plans a Moon Lander

ESA is planning to land a probe in a lunar south polar crater by the end of this decade.  The landing site would be in an area of possible water ice.   ESA’s article on the mission lists the goals as “that it uses the latest navigation technology to fly a precise course from lunar orbit to the surface and touch down safely and accurately. On the way down, it must image the surface and recognize dangerous features by itself, using its own ‘intelligence’.  Then the Lander shall investigate this unique region with a suite of instruments. It will investigate the properties and possible health effects of radiation and lunar dust on future astronauts, and it will examine the soil for signs of resources that could be used by human explorers.”  The next step will be to further develop possible designs over the next 18 months.

Editorial Thoughts: I was unable to find much information on this lander and its goals.  This appears to be a technology development program run by ESA's Directorate of Human Spaceflight.  In its scope and goals, it appears to be similar to the proposed series of NASA Precursor missions that will prove new technologies and investigate possible locations for future manned flights.  Because the mission apparently will investigate sites with lunar ice, it has the potential of producing some good, original science.

Resources:

ESA article on the moon lander http://www.esa.int/esaCP/SEM83CIK97G_index_0.html

Information on the overall program http://www.esa.int/esaCP/SEMBM4CDNRF_Life_0.html  

Lander design concepts from http://www.esa.int/esaCP/SEM83CIK97G_index_1.html#subhead3

JEO & JGO Jupiter Science - Overview

The two spacecraft planned for the Europa Jupiter System Mission -- NASA's Jupiter Europa Orbiter (JEO) and ESA's Jupiter Ganymede Orbiter (JGO) -- will focus on in-depth studies of those two moons with intensive studies conducted from orbit around their respective targets.  Both craft will spend 2-3 years in orbit around Jupiter before settling into their final orbits around their destination moons.  During that time, they can replicate science that Cassini has been performing for the Saturn system.  Jupiter has already had one orbiting spacecraft, Galileo, but it had mid-1970's technology instruments and a crippled antenna that reduced the data return to a bare trickle.  These two planned missions will have 2010's technology instruments and high data rate X-band and Ka-band communications.

This is the first of several blogs that will look at the science these two missions can perform prior to their ultimate investigations in orbit around their respective moons.  The missions studies that previously have been carried out focused on the studies from orbit, with only minimal attention to studies of the moons from flybys and of Jupiter from orbit.  That is beginning to change as the missions undergo further definition.

I believe that looking at what these missions can do prior to their Europa and Ganymede orbit science campaigns is instructive for three reasons.  First, both missions can carry out synoptic studies of the weather of Jupiter.  The Juno mission will study the interior of Jupiter and the weather in slices that will be tiny both in spatial and temporal coverage.  These two follow on missions can study the entire planet's weather for years.  Second, Io and Callisto will be studied only from flybys and distant observations.  The MESSENGER flybys of Mercury has shown what kinds of science can be performed by a modern suite of instruments.  And third, the present mission concepts are not guaranteed to fly.  NASA's mission is subject to prioritization by the Decadal Survey.  ESA's mission is in competition with two attractive astronomy missions for funding.  Supply problems for NASA with plutonium-238 to power their craft may force a radical restructuring of the mission with the result that more focus goes to remote studies.

The February OPAG meeting had several presentations on planning for the current mission concepts, with greater focus on NASA's mission (OPAG is a NASA-chartered group).  The presentations state that the current mission designs are preliminary and have had limited attention.  They suggest that the oribital tours are likely to be considerably refined as mission definition continues.

Click on any image for a larger version.

Currently envisions mission timelines. (From http://www.lpi.usra.edu/opag/feb2010/presentations/GreeleyEtal.pdf)

Example JEO tour showing satellite encounters and distance and phase angles from Jupiter.  This tour design includes an Io science campaign (four science flybys) and a system science campaign that includes numerous remote observations of Jupiter and Io as well as flybys of the other Galilean moons.  JEO will also conduct magnetospheric studies (not shown). (From http://www.lpi.usra.edu/opag/feb2010/presentations/GreeleyEtal.pdf)

Example JGO tour with Ganymede and Callisto flybys and extensive monitoring of Jupiter and the magnetosphere. (From http://www.lpi.usra.edu/opag/feb2010/presentations/GreeleyEtal.pdf)

Example activities for one JEO orbit that includes a flyby of Ganymede and remote monitoring of Jupiter and Io.  The JEO and JGO spacecraft will be able to probe the atmosphere of Jupiter by tracking each other's radio waves as they pass behind Jupiter as seen by the other craft.  (From http://www.lpi.usra.edu/opag/feb2010/presentations/LockScienceScenarioModeling.pdf)

A science definition team (SDT) has been looking into issues relating to the current mission design.  Some items they suggest for further consideration include:

• Could the orbital tours be modified so that the apoapsis of some orbits occur on the day side of Jupiter?  This would allow exploration of additional portions of the magnetosphere and allow longer observations of the daylit side of Jupiter. 
• Can the orbital inclination be increased to allow observation of Jupiter's poles, the rings, and better coverage of the magnetosphere?

Editorial Thoughts: Either of these missions has the potential to do considerable Jupiter system science.  That science could be considerably enhanced if the Jupiter tour prior to beginning the orbit of the their target moons was extended.  This has been propsosed for JEO if the JGO mission were to launch later than expected.  The synergistic science opportunities with two orbiters is great enough that NASA is willing to consider lingering longer in orbit around Jupiter to wait for JGO rather than rushing to orbit Europa.  Should the JGO mission not be selected, extending the JEO Jupiter tour would make good science sense.  An extra year or two could enable a number of additional flybys of Ganymede and Callisto to partially make up the loss of the science from the JGO mission.  However, NASA has to balance this against the increased risk of a malfunction on the JEO craft if it delays its final science campaign at Europa.