Note: While I'm traveling this month with only occasional short access to the internet, I'm reading through some of the back log of proposed mission concepts. I'll post short summaries of the more interesting ideas. Unfortunately, I'm unlikely to have time to search down internet sites to provide hot links to the abstracts and presentations I'm reading. I'll try to provide sufficient information on each that you hopefully can easily do a search to find the original documents.
In this post, I'll a mission concept for the Discovery program (~$425M PI cost, ~$800M fully burdened cost) that would explore the interior of a comet.
The proposal was described in an extended abstract (2 pages) for this year's 41st Lunar and Planetary Science Conference.
Deep Interior Radar Imaging of Comets
LPSC abstract 2670.pdf
One surprise of our exploration of asteroids and the tiny moons of Mars is that many small bodies appear to be rubble piles loosely held together by gravity. We know little about the interior of comets (fast, distant flybys produce poor gravity measurements). However, as the authors of the abstract state, the early reconnaissance of comets "has so far yielded the discovery of an unanticipated range of diversity in geomorphic forms: multiplicities of pits, craters with vertical overhangs, global scale layering, mesas and plains. It has also revealed new geological processes that are revolutionizing our concepts of the cometary interior -- the discovery of repetitive mini-outburts, of patches of enhanced H2O ice, and of caldera-like depressions and smooth flows... It is time to capitalize on these discoveries by moving into a new, detailed exploratory phase where we learn how comets work."
The authors propose to use ice penetrating radar to produce images of the interior of a comet with 10 m resolution that would be comparable to a "medical ultrasonographic brightness scan." Ice and ground penetrating radars have a long heritage both from airplanes for Earth studies and at Mars where they have successfully explored the upper few kilometers of the Martian crust. For a small comet -- the proposed target is the 3 km diameter 79P/duToit-Hartley comet -- the radar could study the entire interior as the spacecraft orbits the spinning comet.
The authors note that the Rosetta mission will conduct an inital probe of the interior of a comet as it tracks radio waves from its Philae lander through the body of a comet. They imply that radar would offer superior interior imaging, but acknowledge the contribution the Rosetta mission will make.
The authors do not state whether or not they have proposed this mission for the current Discovery mission selection.
Editorial thoughts: I don't know if the radar system required for this mission is so costly that a dedicated mission would be needed. Ice penetrating radars come in different flavors. The radar proposed for NASA's Jupiter Europa Mission, for example, is a more capable and massive (and mass tends to be strongly correlated with instrument cost) than the radar proposed for ESA's Jupiter Ganymede Mission. It would seem to me that a spacecraft capable of additional studies such as surface imaging and compositional studies of emitted gases and dust in addition to the radar instrument would be a very attractive mission. However, the radar unit may be too costly for a Discovery-class mission to fly additional instruments. The abstract does not provide any information on this.
I have also been struck by the diversity of comet surfaces we have seen from the few flyby spacecraft to date. Their interiors may be equally varied. It may be that rather than one mission providing a definitive answer, ice penetrating radar may be needed on a number of comet missions before we begin to understand that variety and the processes that created it.
Showing posts with label Discovery Missions. Show all posts
Showing posts with label Discovery Missions. Show all posts
Thursday, September 16, 2010
Tuesday, September 7, 2010
Lunette: Reducing Network Mission Costs
Note: While I'm traveling this month with only occasional short access to the Internet, I'm reading through some of the back log of proposed mission concepts. I'll post short summaries of the more interesting ideas. Unfortunately, I'm unlikely to have time to search down Internet sites to provide hot links to the abstracts and presentations I'm reading. I'll try to provide sufficient information on each that you can easily do a search to find the original documents.
In this post, I'll a mission concept for the Discovery program (~$425M PI cost, ~$800M fully burdened cost) that would explore the moon's interior.
The proposal was described in an extended abstract (2 pages) for this year's 41st Lunar and Planetary Science Conference.
Lunnette: Establishing a lunar geophysical network without nuclear power through a Discovery-class mission
LPSC abstract 2710.pdf
Studies of the interiors of the moon and planets has been repeatedly prioritized by review panels prioritizing future planetary exploration. Planets and large moons have had complex interactions between the formation, evolution, and current state of their interiors and surfaces and, where they exist, their atmospheres. While surfaces and interiors have received considerable attention, interiors have received much less investigation. Gravity measurements from orbiters and flybys provide some information on interiors, but seismic and heatflow measurements are considered essential to extend our knowledge. To date, only the moon has been investigated by a network of surface stations left by the Apollo astronauts. Those instruments represent decade old technologies and were placed at sites chosen for surface geology rather than optimizing the design of the network.
The Lunette proposal attempts to address one of the major roadblocks to establishing surface networks, cost. The current leading proposal for an initial four node lunar network, the International Lunar Network (ILN), reportedly would cost more than a New Frontiers mission (~$650M PI cost, ~$1.2B fully burdened cost). I've seen estimates for a four node Mars network in the range of $1.5B.
The Lunette proposal would minimize costs through three strategies. First it would use solar power in place of nuclear power and would "use new power management technology" to survive and operate through the long lunar night for at least two years of operation. Second, it would place just three nodes on the surface instead of ILN's four. And third, it would depend on international partners to supply and pay for a very broad band seismometer that would be an order of magnitude more sensitive than the Apollo seismometers, a short period seismometer, and a heat flow probe. U.S. scientists would supply a low-frequency electromagenetic sounding instrument and a laser retroreflector.
Editorial thoughts: Studying planetary interiors is important. Two NASA missions in development, the JUNO Jupiter orbiter and the GRAIL lunar orbiters would study the interiors of their bodies using gravity and magnetometer measurements. Studying the interiors of the moon and Mars from the surface is the next logical step. If the Lunette team has found ways to dramatically reduce costs for surface networks, that would be welcome news. The list of authors includes two authors from JPL, suggesting that the engineering analysis may be reasonably advanced. (I don't recognize these author's names and so don't know if they are on the science or engineering side of JPL, and I can't do a web search from the tent I'm writing this in.) On the other hand, the costs of many Discovery proposals reportedly have proven to have under estimated costs in the eyes of the panels that review the proposals. Getting a network mission into even the cost cap of a New Frontiers mission would still be a significant achievement, though. The Lunette proposal sounds like solid progress in that direction.
In this post, I'll a mission concept for the Discovery program (~$425M PI cost, ~$800M fully burdened cost) that would explore the moon's interior.
The proposal was described in an extended abstract (2 pages) for this year's 41st Lunar and Planetary Science Conference.
Lunnette: Establishing a lunar geophysical network without nuclear power through a Discovery-class mission
LPSC abstract 2710.pdf
Studies of the interiors of the moon and planets has been repeatedly prioritized by review panels prioritizing future planetary exploration. Planets and large moons have had complex interactions between the formation, evolution, and current state of their interiors and surfaces and, where they exist, their atmospheres. While surfaces and interiors have received considerable attention, interiors have received much less investigation. Gravity measurements from orbiters and flybys provide some information on interiors, but seismic and heatflow measurements are considered essential to extend our knowledge. To date, only the moon has been investigated by a network of surface stations left by the Apollo astronauts. Those instruments represent decade old technologies and were placed at sites chosen for surface geology rather than optimizing the design of the network.
The Lunette proposal attempts to address one of the major roadblocks to establishing surface networks, cost. The current leading proposal for an initial four node lunar network, the International Lunar Network (ILN), reportedly would cost more than a New Frontiers mission (~$650M PI cost, ~$1.2B fully burdened cost). I've seen estimates for a four node Mars network in the range of $1.5B.
The Lunette proposal would minimize costs through three strategies. First it would use solar power in place of nuclear power and would "use new power management technology" to survive and operate through the long lunar night for at least two years of operation. Second, it would place just three nodes on the surface instead of ILN's four. And third, it would depend on international partners to supply and pay for a very broad band seismometer that would be an order of magnitude more sensitive than the Apollo seismometers, a short period seismometer, and a heat flow probe. U.S. scientists would supply a low-frequency electromagenetic sounding instrument and a laser retroreflector.
Editorial thoughts: Studying planetary interiors is important. Two NASA missions in development, the JUNO Jupiter orbiter and the GRAIL lunar orbiters would study the interiors of their bodies using gravity and magnetometer measurements. Studying the interiors of the moon and Mars from the surface is the next logical step. If the Lunette team has found ways to dramatically reduce costs for surface networks, that would be welcome news. The list of authors includes two authors from JPL, suggesting that the engineering analysis may be reasonably advanced. (I don't recognize these author's names and so don't know if they are on the science or engineering side of JPL, and I can't do a web search from the tent I'm writing this in.) On the other hand, the costs of many Discovery proposals reportedly have proven to have under estimated costs in the eyes of the panels that review the proposals. Getting a network mission into even the cost cap of a New Frontiers mission would still be a significant achievement, though. The Lunette proposal sounds like solid progress in that direction.
Wednesday, June 16, 2010
AVIATR Titan Plane Details
Click on image to go to site for full poster plus additional posters.
A video of a presentation on the mission from a meeting last January has been posted on the web. Together with a recently posted meeting abstract, more information on the science of the mission is now available. Some key facts:
Total plane mass: 125 kg
Science payload mass: 12 kg
Total returned data: ~2Gbytes
Compared to previously proposed balloon missions (both the 2006 $1B Box study and the Titan Saturn System Mission (TSSM) proposal), this mission has some compromises. The science payload is about half of what the balloons would have carried (see table below). Some key instruments such as a mass spectrometer to study atmospheric composition and a radar sounder are not included in the AVIATR proposal. The TSSM balloon mission would have returned far more data, but that was contingent on the presence of a flagship orbiter to relay data. The data rate of the AVIATR mission appears to be similar to that of the $1B Box study balloon platform, which would have sent data directly to Earth. However, almost twice as much data would be returned by AVIATR because the balloon would spend half its time facing away from Earth when it would have been on the night side of Titan.
Instruments proposed for the AVIATR plane and the TSSM balloon platform
On the other hand, being able to actively manuever gives AVIATR some key advantages over a balloon. When AVIATR reaches a target location, it can climb high and fly a grid pattern to take context images of the entire area. Then it can drop down to ~3.5 km to take high resolution images of portions of the area.
To make the most use of the 2GB of data return, AVIATR would send thumbnail images back to Earth. Scientists would then select the most interesting images for full transmission, and AVIATR would use data compression to make maximum use of the bandwidth. A similar scheme was used for the Galileo mission, which had to deal with a similarly constrained data rate due to a malfunctioning antenna.
The cost of the AVIATR mission is described as either Discovery class (~$800M) or New Frontiers class (~$1.2B). (These are fully burdened costs derived from dividing the proposed decadal budget for these programs by the number of expected missions. The costs include the ~$450M and ~$650M, respectively, allocated to the principal investigator plus launch vehicle and presumably other overhead.) The $1B Box study estimated the cost a standalone balloon mission at ~$1.4B using what appears to be similar accounting methods but in FY06 dollars.
Editorial Thoughts: I do believe that we should continue the exploration of Titan and Enceladus in the coming decade. Currently, the flagship mission slot is given to the Jupiter Europa Orbiter over the Titan Saturn System Mission (a decision I agree with, but one the Decadal Survey could overturn). In my opinion, portions of the TSSM proposed mission should be flown: An Enceladus multi-flyby (and possible orbiter) mission that would also study Titan in a series of flybys, a Titan lake lander a la the proposed TIME mission, and either a Titan balloon or airplane mission. There are indications that all of these components individually could be in the Discovery to New Frontier mission class. Ideally, this would be an international effort with more than one space agency contributing the mission elements. I would like to see the balloon or plane carried to Titan by the Enceladus Saturn orbiter that would also act as a data relay and enable substantially more than 2GB of data to be returned.
If a balloon or plane mission were to be flown, I'd prefer the plane mission. The plane could better study the surface by flying to chosen locations of high interest rather than depending on the fate of wind direction. To partially make up for the limited atmospheric instruments in the plane mission, the Titan lake lander could perform atmospheric chemistry measurements during its descent.
Sunday, April 11, 2010
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
"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
Sunday, December 13, 2009
Next Discovery Mission Draft AO Released
NASA has released a draft of its Announcement of Opportunity (AO) for the next Discovery mission. Release of the final AO typically follows in a few weeks to a handful of months based on comments from the proposer community on the draft.
This promises to be a rich set of proposed missions. Possible missions that have been discussed publicly and described in this blog include:
Venus Radar Mission
Comet Coma Rendezvous Sample Return
Trojan Asteroid Rendezvous
Titan Mare Explorer
CHopper
Venus Balloon
Io Volcano Explorer
There are likely to be dozens of other ideas proposed, especially since the cost cap has been raised by not including the launch vehicle in the Principle Investigator's (PI) budget and by the possibility of using a plutonium power source (the ASRG) at no cost to the PI.
Personally, I can't find a favorite among the concepts that have been discussed publicly. All are excellent, and I expect that many that haven't been discussed would be equally good.
What follows are selected quotes from the 133 page draft AO to give a flavor of what NASA is looking for the proposers to do. You can read the entire draft AO at http://nspires.nasaprs.com/external/viewrepositorydocument/cmdocumentid=214565/Discovery%2010%20DRAFT%20RELEASE.pdf
The National Aeronautics and Space Administration (NASA) Science Mission Directorate (SMD) is releasing this Announcement of Opportunity (AO) to solicit Principal Investigator (PI) led planetary science investigations for the Discovery Program.
NASA expects to select one Discovery mission to proceed into Phase B (or an extended Phase A) and subsequent mission phases. The selected mission’s primary launch date shall be no later than the end of calendar year 2016.
One of NASA’s strategic goals is to “Advance scientific knowledge of the origin and history of the solar system, the potential for life elsewhere, and the hazards and resources present as humans explore space...” The NASA Science Mission Directorate (SMD) is addressing this strategic goal by conducting a program of planetary science designed to answer the following science questions:
The cap on the PI-Managed Mission Cost for a Discovery mission is $425M in Fiscal Year (FY) 2010 dollars, not including the cost of the standard launch vehicle (LV) or any contributions (Section 4.3.1 and Section 5.6.1). The cap may be increased through the optional use of specific NASA-developed technologies.
Proposed investigations will be evaluated and selected through a two-step competitive process. Step 1 is the solicitation, submission, evaluation, and selection of proposals prepared in response to this AO. As the outcome of Step 1, NASA intends to select approximately three Step 1 proposals and issue awards (provide funding to NASA Centers and the Jet Propulsion Laboratory (JPL), award contracts to non-NASA institutions, or utilize other funding vehicles, as applicable) to the selected proposers to conduct Phase A concept studies and submit Concept Study Reports to NASA. Step 2 is the preparation, submission, evaluation, and continuation decision (downselection) of the Concept Study Reports. As the outcome of Step 2, NASA intends to continue a single investigation into the subsequent phases of mission development for flight and operations.
The following schedule describes the major milestones for this AO:
AO Release Date (target) ....................................................NLT Early 2010
Preproposal Conference ......................................................2-4 weeks after AO release
Notice of Intent to Propose Deadline ..................................4 weeks after AO release
Proposal Submittal Deadline at 4:30 p.m. Eastern Time ....3 months after AO release
Letters of Commitment due (with proposal) .......................3 months after AO release
Step 1 Selections announced (target) ..................................9 months after AO release
Initiate Phase A Concept Studies (target) ...........................1 month after selection
Phase A Concept Study Reports due (target) ......................10 months after selection
Downselection of investigation(s) for flight (target) ..........16 months after selection
Launch Deadline .................................................................NLT December 31, 2016
This promises to be a rich set of proposed missions. Possible missions that have been discussed publicly and described in this blog include:
Venus Radar Mission
Comet Coma Rendezvous Sample Return
Trojan Asteroid Rendezvous
Titan Mare Explorer
CHopper
Venus Balloon
Io Volcano Explorer
There are likely to be dozens of other ideas proposed, especially since the cost cap has been raised by not including the launch vehicle in the Principle Investigator's (PI) budget and by the possibility of using a plutonium power source (the ASRG) at no cost to the PI.
Personally, I can't find a favorite among the concepts that have been discussed publicly. All are excellent, and I expect that many that haven't been discussed would be equally good.
What follows are selected quotes from the 133 page draft AO to give a flavor of what NASA is looking for the proposers to do. You can read the entire draft AO at http://nspires.nasaprs.com/external/viewrepositorydocument/cmdocumentid=214565/Discovery%2010%20DRAFT%20RELEASE.pdf
The National Aeronautics and Space Administration (NASA) Science Mission Directorate (SMD) is releasing this Announcement of Opportunity (AO) to solicit Principal Investigator (PI) led planetary science investigations for the Discovery Program.
NASA expects to select one Discovery mission to proceed into Phase B (or an extended Phase A) and subsequent mission phases. The selected mission’s primary launch date shall be no later than the end of calendar year 2016.
One of NASA’s strategic goals is to “Advance scientific knowledge of the origin and history of the solar system, the potential for life elsewhere, and the hazards and resources present as humans explore space...” The NASA Science Mission Directorate (SMD) is addressing this strategic goal by conducting a program of planetary science designed to answer the following science questions:
- How did the Sun’s family of planets and minor bodies originate?
- How did the Solar System evolve to its current diverse state?
- What are the characteristics of the solar system that lead to the origin of life?
- How did life begin and evolve on Earth and has it evolved elsewhere in the solar system?
- What are the hazards and resources in the solar system environment that will affect the extension of human presence in space?
The cap on the PI-Managed Mission Cost for a Discovery mission is $425M in Fiscal Year (FY) 2010 dollars, not including the cost of the standard launch vehicle (LV) or any contributions (Section 4.3.1 and Section 5.6.1). The cap may be increased through the optional use of specific NASA-developed technologies.
- The cost of standard launch services is not included within the cap on the PI-Managed Mission Cost, but mission-unique launch services and the differential cost of more capable LVs than the standard LV will be included in the PI-Managed Cost.
- The minimum reserve level of 25% is now assessed against the Phase A-E cost rather than the Phase A-D cost.
- Proposal of investigations enabled by the use of Advanced Stirling Radioisotope Generators (ASRGs) is allowed (Section 5.9.3). ASRGs are provided as Government Furnished Equipment (GFE).
- New propulsion technology has been developed by NASA and is available for infusion into Discovery missions [an advanced ion propulsion engine (NEXT), Advanced Material Bi-propellant Rocket (AMBR) and aerocapture].
Proposed investigations will be evaluated and selected through a two-step competitive process. Step 1 is the solicitation, submission, evaluation, and selection of proposals prepared in response to this AO. As the outcome of Step 1, NASA intends to select approximately three Step 1 proposals and issue awards (provide funding to NASA Centers and the Jet Propulsion Laboratory (JPL), award contracts to non-NASA institutions, or utilize other funding vehicles, as applicable) to the selected proposers to conduct Phase A concept studies and submit Concept Study Reports to NASA. Step 2 is the preparation, submission, evaluation, and continuation decision (downselection) of the Concept Study Reports. As the outcome of Step 2, NASA intends to continue a single investigation into the subsequent phases of mission development for flight and operations.
The following schedule describes the major milestones for this AO:
AO Release Date (target) ....................................................NLT Early 2010
Preproposal Conference ......................................................2-4 weeks after AO release
Notice of Intent to Propose Deadline ..................................4 weeks after AO release
Proposal Submittal Deadline at 4:30 p.m. Eastern Time ....3 months after AO release
Letters of Commitment due (with proposal) .......................3 months after AO release
Step 1 Selections announced (target) ..................................9 months after AO release
Initiate Phase A Concept Studies (target) ...........................1 month after selection
Phase A Concept Study Reports due (target) ......................10 months after selection
Downselection of investigation(s) for flight (target) ..........16 months after selection
Launch Deadline .................................................................NLT December 31, 2016
Tuesday, November 3, 2009
Proposed Discovery Venus Radar Mission
A few posts ago (http://futureplanets.blogspot.com/2009/10/venus-new-frontiers-radar-mapping.html), I wrote about proposed radar missions to remap Venus at higher resolution. At that time, the idea of doing this within a New Frontiers budget (~$650M) was an eye opener for me. I listened into part of the most recent VEXAG meeting, and learned of a Discovery mission (~$425M) that could remap Venus.
The principle investigator, Dr. Sharpton, sent me the following synopsis of the mission: "RAVEN, utilizes the latest in the RADARSAT lineage, extending back to 1996 (RADARSAT 1 launched in Nov. '95). We can accomplish reconnaissance level mapping of Venus at 30-m/px and map about 25% of Venus each cycle (a venusian day). Alternatively, we could map about 3% of the planet at 3-m resolution each cycle. Obviously, we would want to have a combination of resolution modes and have overlap so that we can extract topography. Topographic resolutions would be on the order of 20m vertical resolution and either 300-m postings (if using 30-m images) or 30-m postings (with 3-m images). If InSAR turns out to be feasible (we believe it will), the vertical resolutions would drop to a meter or less."
Dr. Sharpton pointed me to an AGU abstract about the mission. Since there is no easy way to link to AGU abstracts, I'm posting parts of it below. You can search for it and other planetary abstracts athttp://agu-fm09.abstractcentral.com/planner
RAVEN – High-resolution Mapping of Venus within a Discovery Mission Budget
V. L. Sharpton1; R. R. Herrick1; F. Rogers2; S. Waterman3
1. University of Alaska Fairbanks, Fairbanks, AK, USA.
2. The Boeing Company, Huntington Beach, CA, USA.
3. Alliance Spacesystems, Boulder, CO, USA.
It has been more than 15 years since the Magellan mission mapped Venus with S-band synthetic aperture radar (SAR) images at ~100-m resolution. Advances in radar technology are such that current Earth-orbiting SAR instruments are capable of providing images at meter-scale resolution. RAVEN (RAdar at VENus) is a mission concept that utilizes the instrument developed for the RADARSAT Constellation Mission (RCM) to map Venus in an economical, highly capable, and reliable way. RCM relies on a C-band SAR that can be tuned to generate images at a wide variety of resolutions and swath widths, ranging from ScanSAR mode (broad swaths at 30-m resolution) to strip-map mode (resolutions as fine as 3 m), as well as a spotlight mode that can image patches at 1-m resolution. In particular, the high-resolution modes allow the landing sites of previous missions to be pinpointed and characterized... Our current estimates indicate that within an imaging cycle of one Venus day we can image 20-30 percent of the planet at 20–30-m resolution and several percent at 3-5 m resolution. These figures compare favorably to the coverage provided by recent imaging systems orbiting Mars. Our strategy calls for the first cycle of coverage to be devoted to imaging large geographic areas (e.g., Thetis Regio) at 20–30-m resolution with interleaved observation of pre-selected targets at high resolution. The second cycle will include additional imaging, but the focus will be repeat-pass coverage to obtain topography for a significant fraction of the first-cycle targets... All components of the spacecraft are expected to remain operational well beyond the nominal mission time, so global mapping at 10 m or better resolution during an extended mission is conceivable."
The principle investigator, Dr. Sharpton, sent me the following synopsis of the mission: "RAVEN, utilizes the latest in the RADARSAT lineage, extending back to 1996 (RADARSAT 1 launched in Nov. '95). We can accomplish reconnaissance level mapping of Venus at 30-m/px and map about 25% of Venus each cycle (a venusian day). Alternatively, we could map about 3% of the planet at 3-m resolution each cycle. Obviously, we would want to have a combination of resolution modes and have overlap so that we can extract topography. Topographic resolutions would be on the order of 20m vertical resolution and either 300-m postings (if using 30-m images) or 30-m postings (with 3-m images). If InSAR turns out to be feasible (we believe it will), the vertical resolutions would drop to a meter or less."
Dr. Sharpton pointed me to an AGU abstract about the mission. Since there is no easy way to link to AGU abstracts, I'm posting parts of it below. You can search for it and other planetary abstracts athttp://agu-fm09.abstractcentral.com/planner
RAVEN – High-resolution Mapping of Venus within a Discovery Mission Budget
V. L. Sharpton1; R. R. Herrick1; F. Rogers2; S. Waterman3
1. University of Alaska Fairbanks, Fairbanks, AK, USA.
2. The Boeing Company, Huntington Beach, CA, USA.
3. Alliance Spacesystems, Boulder, CO, USA.
It has been more than 15 years since the Magellan mission mapped Venus with S-band synthetic aperture radar (SAR) images at ~100-m resolution. Advances in radar technology are such that current Earth-orbiting SAR instruments are capable of providing images at meter-scale resolution. RAVEN (RAdar at VENus) is a mission concept that utilizes the instrument developed for the RADARSAT Constellation Mission (RCM) to map Venus in an economical, highly capable, and reliable way. RCM relies on a C-band SAR that can be tuned to generate images at a wide variety of resolutions and swath widths, ranging from ScanSAR mode (broad swaths at 30-m resolution) to strip-map mode (resolutions as fine as 3 m), as well as a spotlight mode that can image patches at 1-m resolution. In particular, the high-resolution modes allow the landing sites of previous missions to be pinpointed and characterized... Our current estimates indicate that within an imaging cycle of one Venus day we can image 20-30 percent of the planet at 20–30-m resolution and several percent at 3-5 m resolution. These figures compare favorably to the coverage provided by recent imaging systems orbiting Mars. Our strategy calls for the first cycle of coverage to be devoted to imaging large geographic areas (e.g., Thetis Regio) at 20–30-m resolution with interleaved observation of pre-selected targets at high resolution. The second cycle will include additional imaging, but the focus will be repeat-pass coverage to obtain topography for a significant fraction of the first-cycle targets... All components of the spacecraft are expected to remain operational well beyond the nominal mission time, so global mapping at 10 m or better resolution during an extended mission is conceivable."
Wednesday, October 14, 2009
Titan Mare Probe
Space.com has an article on the proposed Titan Mare Explorer that would float a probe on one of that moon's seas. I believe that all the material in the article has been presented in this blog, but it makes a nice read. http://www.space.com/businesstechnology/091014-titan-boat-mission.html
Tuesday, September 29, 2009
Comet Coma Rendezvous Sample Return (CCRSR) Mission Concept
This blog entry continues both at looking at white papers on missions to the solar system's small, primitive bodies and to continue the occasional series of mission concepts in development to use ASRG plutonium power supplies. In the former series, you'll remember that the number one priority mission for comet exploration in the coming decade is a warm sample return (more on the warm part, later). In the latter series, NASA has developed a new electrical power supply system that uses much less plutonium that the old RTGs or MMRTGs. The agency is ea gar to test the ASRGs on a flight mission, and has funded 12 mission concept studies to explore what types of Discovery missions ($450M) these power supplies would enable.
Comets are believed to be the least altered bodies in the solar system, preserving both the mineral (in dust form) and volatiles present at the birth of our solar system. Returning samples to be studied in terrestrial laboratories has been a high priority for the scientific community. The Stardust mission partially fulfilled that goal by collecting dust particles during a high velocity flyby of comet Wild 2. The brief nature of the encounter and the high velocity limited the number of dust particles collected and the types of particles that could survive the high speed impact with the sample collectors.
Ultimately, the goal is to land on a comet, collect a sample containing both dust and volatiles, and return the frozen sample to year. Frozen is the key. Volatiles that melt will undergo various chemical reactions that will alter the samples. Unfortunately, such a mission is bedeviled by questions of both how to collect the samples (what is the surface a comet like and once we land on one, is that a good guide to all comets?) and of how to keep samples frozen well below the freezing point of water within a small re-entry capsule (even during the descent through Earth's atmosphere). This class of mission has been put off to the following decade with a goal of advancing the technology in the coming decade.
An alternative mission would collect a sample and allow the volatiles to warm during the return voyage and plummet through Earth's atmosphere. The dust particles would be unaffected by the warming, and the melted and altered volatiles would still provide clues. Such a mission might be possible in the New Frontiers program ($650M).
CCRSR takes a different approach. It would not land on a comet, but would instead make multiple passes through a comet's coma and jets. The encounter with dust particles would be at low speeds, preserving fragile samples. No volatiles would be collected, but a mass spectrometer would measure their composition in real time. By sampling different jets, the mission may be able to sample different portions of the comet's interior. Multiple collectors will be used so samples from specific jets can be identified. In addition to the mass spectrometer, adust detector (to estimate amounts of samples collected) and wide and narrow angle cameras would be flown.
Editorial Thoughts: This proposal gets around a key problem of sampling any small body: given the wide range of surface materials and surface densities possible, how do you intelligently design a collection system? It falls short of the hoped for goal for this decade to return both dust and volatiles (even if warmed over). Discovery mission opportunities, however, are more frequent than New Frontiers opportunities, so this mission could meet much of the goal at a lower cost and with better chance of selection.
A key goal of the next Discovery mission selection may be to test the ASRG system. Because CCRSR returns to Earth, it would have to jettison its ASRG's in deep space and make the return voyage using solar panels. The white paper suggests that the mission might be possible with only solar panels -- a possible knock in the coming selection.
Link: The Comet Coma Rendezvous Sample Return (CCRSMission Concept - The Next Step Beyond Stardust
Saturday, September 26, 2009
Trojan Asteroid Rendezvous
In the last post, I listed the highest priority missions for asteroid and comet missions. The highest priority New Frontiers mission for main belt and Trojan asteroids was listed as a mission to the Trojan asteroids. (Trojan asteroids share Jupiter's orbit and are found in the L4 or L5 points leading or trailing Jupiter.) An entire white paper is devoted to justifying the high priority given to this mission.
Asteroids, like comets, are believed to be remnants left from the formation of the solar system. For bodies that underwent little heating, they probably contain relatively pristine samples of the materials from which the planets formed. For bodies that underwent significant heating (such as the main belt asteroid Vesta) they may preserve the record of processes by which the early planets formed.
Scientists would like to examine asteroids from a variety of locations in the solar system as a way to probe the gradient of conditions and materials believed to have been present during planet formation. Two theories exist as to the original location of the Trojan asteroids. The simplest would have that they formed where they are now, in which case they record conditions where Jupiter and its moons formed. A new theory, however, suggests that the four giant outer planets migrated from the locations at which they originally formed. In this model, Uranus and Neptune migrated outward into the cometary realm. Most comets would have been ejected from the solar system or pushed out into the Kuiper belt. A small fraction (hundreds of thousands) were thrown inward to become the Trojan asteroids. In this case, the Trojans are easily assessable Kuiper belts worlds.
Telescope studies shed little light on this question because the spectra are featureless, as are the spectra of C-, P-, D-type asteroids and cometary nuclei. Either theory of their formation would suggest that these should be volatile-rich worlds, but the spectral are enigmatic. A spacecraft mission is needed -- preferably to visit a number of bodies -- to resolve these questions.
The Trojan white paper lists two overarching questions for a mission to the Trojan asteroids:
"1. Did the Trojan asteroids originate near Jupiter’s orbit or farther out in the solar system?
2. What do compositions of these primitive bodies tell us about the region(s) of the solar nebula in which they formed?"
These questions would be answered by focusing on a set of specific questions for the body (or preferably, bodies) visited:
"1. How much and what types of ice and organics are present on and within Trojan asteroids?
2. What is the mineralogy of the silicates present on and within Trojans?
3. How do the geological processes that have occurred on the Trojans compare to those that have affected other small bodies?
4. What is the relationship between Trojan asteroids and comets, TNOs, outer planet satellites, and main belt asteroids?
5. Are densities and bulk compositions of Trojans diverse or homogeneous?
6. How are the spectral and physical properties of Trojan surfaces modified over time by the space environment?"
At least one mission concept is being actively developed, a Discovery-class mission that would make use of NASA's new plutonium ASRG power sources to allow flyby, orbital, and landed phases. The summary that follows is from a post done last January.
Ilion Mission Concept
While spacecraft have orbited and landed on near Earth asteroids and flown by main belt asteroids (and the Dawn spacecraft will orbit 2 of the 3 largest main belt asteroids in the next decade), no spacecraft has visited a Jovian Trojan asteroid. Ilion would do that by:
"The Ilion mission will flyby several Trojans and rendezvous and land on one of them. It carries remote sensing instruments to characterize the asteroid’s structure and landed instruments to measure its surface composition. Preliminary orbit calculations have shown that several of the Trojans can be reached by Discovery-class missions with reasonable travel times... Approximately the final 2 years of the cruise will be spent within the L5 Trojan cloud... After [orbit insertion], Ilion will observe the target asteroid for several months and a landing site will be identified. After landing, a variety of compositional and physical measurements can be made."
Resources
While spacecraft have orbited and landed on near Earth asteroids and flown by main belt asteroids (and the Dawn spacecraft will orbit 2 of the 3 largest main belt asteroids in the next decade), no spacecraft has visited a Jovian Trojan asteroid. Ilion would do that by:"The Ilion mission will flyby several Trojans and rendezvous and land on one of them. It carries remote sensing instruments to characterize the asteroid’s structure and landed instruments to measure its surface composition. Preliminary orbit calculations have shown that several of the Trojans can be reached by Discovery-class missions with reasonable travel times... Approximately the final 2 years of the cruise will be spent within the L5 Trojan cloud... After [orbit insertion], Ilion will observe the target asteroid for several months and a landing site will be identified. After landing, a variety of compositional and physical measurements can be made."
Resources
Thursday, September 10, 2009
Thoughts on Titan Mare Explorer
John R. passed along these thoughts (posted with his permission) in response to the blog posts about a proposed Titan Mare Explorer (TIME) (http://futureplanets.blogspot.com/2009/09/titan-mare-explorer-abstract.html and http://futureplanets.blogspot.com/2009/09/titan-mare-explorer-time.html).
Here's a link to a large image of a watery horizon on a cloudy day on Earth:
http://retiredeagle.files.
Makes me think we might want to pass on the imagery.
The chemical analysis is a must, and sounding for depth is too easy not to do, but I seriously wonder the value of a single depth measurement. As I understand it, the weight of water ice under liquid methane would be fairly low in Titan's gravity, so I wonder if the lake bottom might be very heterogeneous, making a point measurement like that sort of arbitrary. A single altimetry track provided by radar, if some wavelength could penetrate the liquid, would be infinitely more useful.
Even the chemical analysis will leave us wondering about anisotropies. The Earth's oceans vary in salinity by a factor of about 1.5 from one location in open water to another. And here's an interesting map of salinity for Lake Pontchartrain.
http://pubs.usgs.gov/of/2002/
All of which is just to flag, mindful of the Galileo Probe's experience at Jupiter, the risk of anisotropies and the impact that has on the value of collecting data. Clearly, the value is still there, and we'd love to have it in hand, but it undermines the meaningfulness of the data to some extent, as long as we're comparison-shopping billion-dollar missions.
Editorial Thoughts: These issues emphasize, in my mind, the value of TIME being able to make measurements over months, which its plutonium power source would allow. That would allow it to examine the surface conditions under varying weather conditions (assuming they vary meaningfully over a few months). If the winds or currents can push the lander (raft? boat?) over a meaningful transect of the surface, then there would be more chances to sample compositional heterogeneity. This would also be useful for depth sounding. I wonder if the probe could be designed so that the structure above the surface would be more likely to catch the wind?
Here's a link to a large image of a watery horizon on a cloudy day on Earth:
http://retiredeagle.files.
Makes me think we might want to pass on the imagery.
The chemical analysis is a must, and sounding for depth is too easy not to do, but I seriously wonder the value of a single depth measurement. As I understand it, the weight of water ice under liquid methane would be fairly low in Titan's gravity, so I wonder if the lake bottom might be very heterogeneous, making a point measurement like that sort of arbitrary. A single altimetry track provided by radar, if some wavelength could penetrate the liquid, would be infinitely more useful.
Even the chemical analysis will leave us wondering about anisotropies. The Earth's oceans vary in salinity by a factor of about 1.5 from one location in open water to another. And here's an interesting map of salinity for Lake Pontchartrain.
http://pubs.usgs.gov/of/2002/
All of which is just to flag, mindful of the Galileo Probe's experience at Jupiter, the risk of anisotropies and the impact that has on the value of collecting data. Clearly, the value is still there, and we'd love to have it in hand, but it undermines the meaningfulness of the data to some extent, as long as we're comparison-shopping billion-dollar missions.
Editorial Thoughts: These issues emphasize, in my mind, the value of TIME being able to make measurements over months, which its plutonium power source would allow. That would allow it to examine the surface conditions under varying weather conditions (assuming they vary meaningfully over a few months). If the winds or currents can push the lander (raft? boat?) over a meaningful transect of the surface, then there would be more chances to sample compositional heterogeneity. This would also be useful for depth sounding. I wonder if the probe could be designed so that the structure above the surface would be more likely to catch the wind?
Wednesday, September 2, 2009
Titan Mare Explorer (TiME)
As I've mentioned in past blog entries, NASA is funding a series of studies of Discovery missions that could make use of the newly developed ASRG plutonium power supplies. One of the most intriguing has been the Titan Mare Explorer (led by Ellen Stofan), which would put a probe on the surface of one of the lakes of Titan. Public information on the proposed mission has been scanty, but an abstract for the upcoming Division of Planetary Sciences meeting provides a few hints (and I'll add a couple of tidbits I've picked up).
From the abstract, "The scientific objectives of the mission are to: determine the chemistry of a Titan sea to constrain Titan’s methane cycle; determine the depth of a Titan sea; characterize physical properties of liquids; determine how the local meteorology over the seas ties to the global cycling of methane; and analyze the morphology of sea surfaces, and if possible, shorelines, in order to constrain the kinetics of liquids and better understand the origin and evolution of Titan lakes and seas."
I've heard through the grapevine that the instrument suite would be limited (as befits a ~$450M mission) to a mass spectrometer, a meteorology and physical properties experiment (probably several instruments in a package), and a descent and surface camera. This may compare favorably with the instrument package that was proposed for the lake lander in the Titan Saturn System Mission flagship proposal -- it's hard to tell without detailed listings of the proposed instruments. One key instrument that I haven't heard of for the proposed Discovery mission would be a gas chromatograph, which would enable detection of complex molecules. The TSSM lake lander had a combined mass spectrometer/gas chromatograph while I've heard of only a mass spectrometer for the proposed Discovery mission. It isn't clear if the gas chromatograph has been dropped, or just isn't listed.
The Discovery proposal calls for, as I understand it, six months of observations as the probe floats on the lake surface with a possible mission extension of several more months. Depending on how far the probe travels on the surface of the lake, this might allow depth measurements along a significant transect and might even bring the probe to a shore.
Editorial Thoughts: This is an exciting mission proposal. I'd love to see images from the surface of an alien ocean. The measurements of the lake composition would greatly advance our understanding of Titan chemistry.
However, there are some caveats to keep in mind. Data relay would be direct to Earth. Think of tens to hundreds of bits per second, most likely. We are unlikely to get great panoramas of photos. Think postage stamp images. Secondly, Titan is a cold place place (to put it mildly). Designing a probe that can reliably survive months on a Discovery budget may prove to be optimistic. Remember that one of the areas of technology development proposed to enable future Titan landers is technology to survive and operate in the frigid climate.
Still, I like this proposal, and hope that it is feasible in a Discovery budget.
Resources: Titan Mare Explorer abstract
From the abstract, "The scientific objectives of the mission are to: determine the chemistry of a Titan sea to constrain Titan’s methane cycle; determine the depth of a Titan sea; characterize physical properties of liquids; determine how the local meteorology over the seas ties to the global cycling of methane; and analyze the morphology of sea surfaces, and if possible, shorelines, in order to constrain the kinetics of liquids and better understand the origin and evolution of Titan lakes and seas."
I've heard through the grapevine that the instrument suite would be limited (as befits a ~$450M mission) to a mass spectrometer, a meteorology and physical properties experiment (probably several instruments in a package), and a descent and surface camera. This may compare favorably with the instrument package that was proposed for the lake lander in the Titan Saturn System Mission flagship proposal -- it's hard to tell without detailed listings of the proposed instruments. One key instrument that I haven't heard of for the proposed Discovery mission would be a gas chromatograph, which would enable detection of complex molecules. The TSSM lake lander had a combined mass spectrometer/gas chromatograph while I've heard of only a mass spectrometer for the proposed Discovery mission. It isn't clear if the gas chromatograph has been dropped, or just isn't listed.
The Discovery proposal calls for, as I understand it, six months of observations as the probe floats on the lake surface with a possible mission extension of several more months. Depending on how far the probe travels on the surface of the lake, this might allow depth measurements along a significant transect and might even bring the probe to a shore.
Editorial Thoughts: This is an exciting mission proposal. I'd love to see images from the surface of an alien ocean. The measurements of the lake composition would greatly advance our understanding of Titan chemistry.
However, there are some caveats to keep in mind. Data relay would be direct to Earth. Think of tens to hundreds of bits per second, most likely. We are unlikely to get great panoramas of photos. Think postage stamp images. Secondly, Titan is a cold place place (to put it mildly). Designing a probe that can reliably survive months on a Discovery budget may prove to be optimistic. Remember that one of the areas of technology development proposed to enable future Titan landers is technology to survive and operate in the frigid climate.
Still, I like this proposal, and hope that it is feasible in a Discovery budget.
Resources: Titan Mare Explorer abstract
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