Wednesday, December 31, 2008
Highlights [with my comments in brackets]:
MSL will stay within its FY09 budget: Overrun will occur in FY10-11 and is expected to be several hundred million dollars [the overrun may be roughly equal to the cost of a Mars Scout mission or a Discovery mission. However, simply canceling the next Scout or Discovery mission wouldn't free up funds in the right years (as I understand the budget) since the peak funding would not occur at the right time]
Several options to handle the MSL cost overrun within the Planetary Science Division have been created: (1) Use the “Guiding Principles” determined by the Planetary Science Subcommittee (PSS); (2) Mars programs effected the most; then the rest of planetary; delaying missions preferable to cancellation [The guiding principles from the last PSS meeting were, "Consistent with concurrent SMD policy, cost increases incurred by the MSL project should, to the extent possible, be borne by JPL, the implementing organization for the mission. Additional funds should be sought next from within the Mars Exploration Program. Impacts to non-Mars programs, as needed after those two sources of funds are utilized, should be sought through delays rather than cancellation of approved missions now under development.]
Only one resulting action so far: The release of NF-3 AO (was to be Feb) is on hold until approved go forward plan is in place [The only silver lining here is that the selection of 2-3 candidate New Frontiers missions (the selection process first picks 2-3 missions for further study from which the final selection will be made) likely will come after the target for the next Flagship mission (Jupiter-Europa or Saturn-Titan) occurs. If Saturn-Titan is selected for the Flagship mission, a proposal to study the moons of Jupiter with a New Frontiers mission might be proposed.]
Flagship mission target selection process and schedule appears to be unchanged: NASA aligned its schedule with ESA: 2018-2022 launch date; Technical implementation/readiness will be critical to decision [Given that the science for both targets is absolutely compelling, I think that technical implementation/readiness will be the deciding factors. Unfortunately for us in the public trying to handicap the selection, we have no insight into these areas.]
Tuesday, December 30, 2008
It would seem unlikely to me that a single mission could include all the elements listed below. However, the hints are interesting to ponder.
NASA is developing potential proposals for the upcoming New Frontiers Program Announcement of Opportunity (2009) that involve multiple strategies for Venus exploration. Many of the suggested mission concepts aim to deliver scientific payloads through the atmosphere of Venus to the surface. Four options are being considered that likely require parachute systems: a lander, a deployed balloon reconnaissance platform, a large probe, and a smaller probe. A key component of these options is a Venus parachute subsystem. It is highly desirable that this subsystem have a strong heritage to previous planetary missions, and especially those implemented in the past 15 years. This announcement supersedes any previously released RFI. Each of the four primary options has a unique set of elements, as summarized below.
For the Venus Lander, the backshell will be ejected and a single canopy will be deployed at an altitude of ~ 65-67 km and a velocity of ~Mach 0.8. The atmospheric entry interface heat shield will be jettisoned after parachute deployment. The Venus Lander is to touch down in approximately 50 minutes from parachute deployment at an impact velocity of less than 10 m/s. The entry vehicle mass (backshell, Lander, and heat-shield) will be 800 to 1000 kg, and the Lander mass will be no more than 695 kg.
For the Balloon Reconnaissance Platform, the backshell will be ejected and a single canopy will be deployed by a mortar at an altitude of ~ 60 km and a velocity of Mach 0.8 to 1.2. The heat shield will be dropped, and approximately 10 seconds after the parachute is deployed, inflation of the balloon will begin. Approximately 30 seconds after the parachute is deployed, the Balloon Reconnaissance Platform will be released from the parachute. The speed at release should be less than 50 m/s.
For the Larger Probe, a mortar will deploy a pilot parachute which will carry off the backshell and deploy the main canopy. This system will utilize a 300-500 kg total flight system mass and deploy the parachute at ~ 60-65 km for later release around 50km. The parachute subsystem will consist of two basic groupings of components: a mortar deployed pilot parachute for backshell separation and main parachute deployment; and a main parachute for heat shield separation and descent speed control. Deployment will occur at a velocity of ~Mach 0.8. The heat shield will be jettisoned approximately 5 seconds after main parachute deployment. The main parachute will be jettisoned at an altitude of 15 to 30 km.
For the Small Probe, a mortar will deploy a single canopy which will carry off the backshell and extract the Small Probe pressure vessel from the aeroshell. This system will utilize a 85-120 kg total flight system mass and deploy the parachute at ~ 60-65 km for later release around 50 km. The parachute subsystem will consist of two basic groupings of components: a mortar deployed pilot parachute for backshell separation and main parachute deployment; and a main parachute for heat shield separation and descent speed control. Other components are similar to the large probes described above.
Monday, December 29, 2008
One downside to news readers for blogs is that it really cuts down on user posted comments. I received the following from Ken today with some questions on reusing the Mars Science Laboratory Skycrane landing system. With Ken's permission, I'm posting his e-mail and my response.
Blogs and blogs have talked about the US’ one shot deals in missions…. There upside and downside and the long prep time to get one launched… obviously budget has something to do with it. And that is where my idea comes into play. Although still not proven…… we are spending a lot of money on it….. so it better work….. what about participating with other countries on future missions by either offering… or better yet, selling the Sky Crane idea? Yes, it has to work first, but we all know the risk in space exploration. I know there is some intl law for this…. But come on!!!
It just seems we always have to re-invent the wheel (with the exception of the landing bags concept for Pathfinder and MER), but lets use our ideas to help mankind explore. If, indeed, we want to continue to lead in the exploration of outer space, that can be done by helping another country get there. ExoMars comes to mind as a perfect oppty to participate. With their recent delays, this gives them more time to adapt the Sky Crane as its landing option instead of airbags. We get to do another mission of this scope instead of waiting another 12 years…..lets face it, MSL will not happen before then…. And we could recoup some money lost in past budget overrides. Now, we put some cameras on the Sky Crane and we get some extra photos at a great perspective.
Again, after reading your blogs, you may know if there is even a breath of this concept going around. Or maybe once again we just let NASA continue these one shot wonders… I mean there has not been any talk of a Sky Crane 2 for another mission.
You have some good ideas here that follow some of mine. A few thoughts:
1) The Skycrane is a very novel idea for landing on Mars. One big problem with landing a rover is how do you get it off the lander? Ramps were used for the MERs, but they rested on a minimal platform enabled by an airbag landing. MSL is too large (as I understand it) for an airbag landing system. So, if you have a powered lander like Phoenix, how do you build a practical set of ramps (you need several in case a boulder or other feature makes one unusable). The Skycrane eliminates that problem. It's too difficult to quickly describe, so here are some links: MSL website, Space.com, and on-going discussion at the Unmanned Spaceflight forum.
2) Right now, NASA's ideas for the next rover mission appear to be just that -- ideas. Preliminary thinking is to use either airbags or the skycrane. Also tied into this is how much to reuse the entire MSL entry and descent system since it allows much more precise targeting of the landing site. This opens up much more Martian terrain to exploration. It is much easier to find a small safe landing location (near some very interesting geologic formations that are not safe landing zones) than a large one.
3) NASA and ESA have said that they will jointly work on a 2016 rover, but nothing has been publicly said about how. One statement from an ESA official is that they want to develop their own expertise in entry and landing. To me, this is not an optimal solution to making the most of tight budgets on both sides of the Atlantic. I think that a superb sharing of expenses and expertise would be for NASA to supply a modified MSL entry and landing system and share its knowledge of the wheel system (a lot of work has been done to optimize that!). ESA would build the rover. NASA would supply data communications either through the (then) old MRO or preferably through a new orbiter, the Mars Science Orbiter. Either NASA or ESA could provide the launch, although my understanding of US technology export laws suggest that it would be legally simpler for NASA to provide the launch (our technology never needs to leave the US).
In addition, ESA's Gaia mission will enable new measurements of the effects of Dark Matter on movement of stars in our galaxy (see Space.com article). This isn't a planetary mission, but it is a neat astronomy mission, so I hope you'll appreciate the link. Let me know through comments or e-mails if you'd like future links to astronomy missions. Contact me at vkane56[at]hotmail[dot]com. (And curses to spammers that keep me from just providing a link to my e-mail!)
Sunday, December 28, 2008
Target for the next New Frontiers Mission
South Pole -- Aitken Basin Sample Return 5 (6%)
Venus in Situ Explorer 32 (42%)
Comet Surface Sample Return 1 (1%)
Network Science 4 (5%)
Trojan/Centaur Reconnaissance 5 (6%)
Asteroid Rover/Sample Return 6 (7%)
Io Observer 23 (30%)
Ganymede Observer 0 (0%)
Total votes = 76
Target for the next Flagship mission
Europa Jupiter System Mission 23 (37%)
Titan Saturn System Mission 38 (62%)
Total votes = 61
Saturday, December 27, 2008
What I found most interesting though was the chart below that showed how mission costs could be plotted as a combination of weight (as a surrogate for design difficulty and cost of procurement, assembly, and test) and mission difficulty. Large missions in the Cassini weight class would range from ~$3B-~$7B depending on mission difficulty. What is immediately obvious is that missions that begin to exploit the launch capabilities of the Constellation system would likely fall in the $5B-$15B range. Such missions would eat up the entire science budget of NASA for years. To a lesser extent, missions using the Delta IV heavy launcher would also dominate the science budget. My reading of this is that the science program is budget constrained, not launch constrained.
Friday, December 26, 2008
NASA has long used plutonium 238 as an electrical power source for missions that could not use or depend on solar power. (The power units use the high heat produced by this isotope to generate power -- they are not nuclear reactors. The correct term is radioisotope power system (RPS)) To date, these have included eight outer planet missions, two Mars surface missions (the Viking landers), and six lunar science stations for the Apollo program. In addition, the Mars Pathfinder and MER rovers have used small amounts of plutonium 238 as heat sources to help keep them warm.
For the future, NASA plans to use plutonium to power the Mars Science Laboratory rover, the next outer planets flagship mission, and possibly a Discovery mission and or New Frontiers mission or two. (At one time, the Solar Probe, which would graze the atmosphere of the sun, was to be plutonium powered, but that mission is now planned to be powered by solar panels.) After that set of missions, it appears that the stockpile of plutonium will be gone.
Unfortunately, plutonium 238 is no longer being manufactured. NASA currently is purchasing plutonium 238 from Russia to enable the future missions listed above., and its stockpiles are unknown (at least publicly) but the expectation seems to be that supply is limited. Production could be restarted, but at a cost of several hundred million dollars, or the price of a planetary mission.
Advances in solar cell technology could somewhat relieve the pressure to use RPS to enable outer planet missions. It appears that solar cells could be used out to 10 AU, which would enable missions to Jupiter, Saturn, and inner Centaur bodies. However, there are issues. Radiation degrades solar cell performance, making the use of solar cells for Jovian missions challenging if the probe is to study Europa or Io. (The solar powered Juno orbiter uses a "hole" in the radiation belt close in to Jupiter plus a short mission lifetime to avoid this problem.) Even when the radiation can be avoided, large solar cell panels add weight, make instrument pointing difficult, and may require battery backups for eclipses and times when the cells cannot be pointed at the sun. For missions to Saturn or Centaur bodies, the power levels available would be low.
In a worst case reading of the situation, the solar system available for exploration could shrink to the inner solar system. Of course, smart people have been working on this issue. The next several posts will deal with ideas to work around the plutonium supply limitations (under the assumption that production doesn't restart).
If you don't want to wait to read more, Emily L. did an excellent write up on the problem and one approach in her blog.
Friday, December 19, 2008
"Ronald Greeley of Arizona State University, Tempe, NASA co-chair of the joint science definition team, declared that "the Europa Jupiter System Mission is essentially ready to go. Of course, the key driver is exobiology." And the theme of the proposed joint mission to the Jupiter system is the emergence of possibly habitable worlds."
"The Titan team's pitch is broader. "There's something on Titan for virtually all aspects of planetary science," was how Jonathan Lunine of the University of Arizona, Tucson, NASA co-chair of the Titan Saturn System Mission (TSSM) science team, described it. The mission would investigate how Titan functions as a system, determine how far prebiotic chemistry has developed, and continue exploring Enceladus with a series of flybys."
"By the end of January, they will jointly select one mission to proceed. They [NASA and ESA] are likely to be balancing the technological ambition of the Titan balloon and the 9-year travel time to Saturn against a science focus on Europa. After that, though, both NASA and ESA have years of maneuvering for funds ahead. NASA will need to navigate around the fallout from MSL; ESA will have to compete its outer planets mission against two astrophysics projects, and both must overcome budgetary woes from the financial crisis. As Green said, an outer planets flagship mission "is not a done deal.""
Let us suppose, however, that Titan is chosen as the destination for the next Flagship mission. That leaves Jupiter's moons as viable targets for future Discovery and New Frontiers missions.
Based on the ground rules of those missions, we would expect that one moon would be the focus (my vote is Io, but there are Ganymede champions, too). We have become used to extended missions that greatly expand on the goals and science of the original mission. Could one mission do the holy grail and explore multiple moons? In theory, the flybys could be done in an extended mission after the initial mission studying Io was completed.
Gravity assists would certainly enhance the possibility of missions that would visit multiple moons. If the craft plans to explore Io, however, and reduce radiation explore by flying a highly inclined orbit, then there is a catch. As I understand the rules of gravity assits, it would be hard to use Io flybys in an inclined orbit to set up subsequent encounters with the other major moons. (Although the mission design wizards might surprise me.) Instead, the craft might have to carry enough fuel to raise the perijove from Io to Europa or Ganymede. That's not impossible. Galileo raised its perijove by a similar amount after entering Jovian orbit. If the orbit was raised to encounter Ganymede, that moon is large enough that the inclination could be lowered to enable encounters with Callisto or Europa. Such a strategy, however, requires the craft to carry the extra fuel, which means a tradeoff of a larger launcher or less payload. It is doubtful that a proposer would suggest making that tradeoff to enable a possible extended mission that might or might not happen.
Another issue is instruments. The priority instruments for Io differ from those for the icy moons. For Io, for example, a thermal imager to map volcanic activity is a high priority. Its a much lower priority for the icy moons where it would be used to search for any hot spots. (Hot being relative on frigidly cold moons.) For the icy moons, near infrared spectrometers and ice penetrating radars are higher priority instruments. The infrared spectrometer is a mid-priority instrument for Io, and I haven't seen the radar listed as a priority for this world. The tension on instrument payloads extends to the details. Cameras typically carry filters to image in specific spectral wavelengths to image specific materials. This is not my field of expertise, but my understanding is that the filters desired for Io and the icy moons differ.
The Io Volcano Observer shows that a very tightly focused Jovian moon mission could be done on a Discovery budget (~$450M including launcher) if NASA relaxes budget constraints (in the case of IVO by supplying the power system at no cost to the proposer). If I read the slides describing the proposal correctly, the budget is very tight, with it unclear whether the imager, for example, would have all the filters that would optimize observations. Useful instruments such as a wide angle camera for stereo images or a near-infrared spectrometer are not on the proposed list and appear as wishes. If we are looking at a mission that would cover the science observations of multiple bodies, then the Discovery budget feels inadequate. We would probably need the resources of a New Frontiers ($650M not including launcher) to do an adequate job.
Europa has clearly been listed as the highest priority Jovian moon. If the next flagship mission goes to Titan, then a Europa observer that would do multiple flybys would logically be the next priority for a Jovian moon mission. The goals of the Europa mission would likely be similar to those of the proposed Ganymede observer. Much more of the moon could be imaged at high resolution than was possible with Galileo. A modern spectrometer (Galileo’s instrument was mid 1970s technology) could possibly determine whether or not ocean material lies near the surface. An ice penetrating radar could sample small transects of the surface during each flyby to test how thick the crust is.
If a Europa observer were to fly, extending the mission to observe Ganymede and Callisto would be easier than with an Io observer. The radiation field at Europa is less intense than at Io, possibly allowing the Jovian orbit to be in the plane of the moons. If so, then it would be easy to use gravity assists to arrange flybys of Ganymede and Callisto. The instruments tuned to study Europa would also be well suited to studying the icy surfaces of those other two moons.
Discovery and New Frontiers spacecraft are implemented under tight budget constraints. Proposing instruments for a possible extended mission would be a gutsy move in a highly competitive environment. I would love to see a proposed New Frontiers Galilean moon observer, which is what would be needed. I doubt that would happen. Instead, any mission proposals for Galilean moon missions are likely to be tightly focused on a single target. So if Titan is selected as the target of the next Flagship mission, then we would want two follow on missions to study the moons. One would be optimized for Io (and most importantly be placed in an orbit to minimize radiation and increase the number of flybys) and then other for the icy moons.
As I waited at the airport, I missed the kickoff of the next planetary Decadal Survey. Modeled on the similar surveys done by the astronomical community, these surveys look at the state of the science, options for future missions, and prioritize NASA's exploration efforts for approximately the next decade. (In a future blog entry, I'll provide a report card on the last Decadal Survey completed in in 2003.) A key goal of this survey, I'm told, is that it will make a strong effort to get much more accurate estimate of costs for its key recommendations. In the last astronomical survey, for example, the cost of the James Webb Space Telescope was severely underestimated. As a result, a number of missions of lower priority have had to be deferred to cover the cost overrun. A similar example in the planetary program might be the Mars Science Lab (MSL), but as explained in a previous entry, the Decadal Survey was recommending a modest technology development mission while the Mars community was recommending a major science mission. (The difference between the two at the time was around $1B.) I am told that the goal is to complete the next Decadal Survey in approximately six months.
I had a long chat with one of the Titan-Saturn Flagship proposal engineers. He explained the major reason that the proposed mission will image Titan at 50 m compared to the state of the art cameras at Mars that image that planet at sub meter resolutions. The Titan atmosphere extends so far into space that the orbiter has to orbit 1500 km above th surface. Compare that to the 250 distance of the Mars Reconnaissance Orbiter. I suspect that additional issues – such as imaging at longer wavelengths (which reduces resolution) and the ubiquitous haze – are contributing issues. (It’s also important to remember that the instruments listed in the proposal are placeholders. The actual instruments to be flown would be selected through a competition. Generally the selected instruments are more capable than the placeholders.)
The mission designer also explained why the orbiter delivers the balloon and lander into the Titan atmosphere months before Titan orbit insertion. This isn't an issue with the lander which will have a surface lifetime of hours. It does create relay issues (but not insurmountable ones) for the balloon. Apparently the weight of the two in situ craft is enough that the mission designers do not want to use to extra fuel that would be caused by carrying them longer.
He also explained why the option of simply launching the balloon and lander separately to arrive after the orbiter is in place at Titan isn't the plan of record. It is cheaper to have a single launch. More importantly, the balloon has its own plutonium power source. ESA's rules apparently prevent it from launching craft with radioactive power sources. NASA doesn't want the cost of a second launch on its books. In theory, ESA could contribute hardware to the orbiter equivalent to NASA's cost of a second launch. However, the ground rules of the proposal stated that NASA would pay for the orbiter and ESA the in situ probes. If Titan is selected as the destination of the Flagship mission, this rule can be re-examined.
And speaking of re-examining the redefinition of the Titan mission, Thomas Spilker dropped some hints. Spilker is one of the mission design wizards at JPL who examines options for future missions. (He's published papers, for example, on options for Neptune orbiters even though those are decades away.) He gave an overview of the challenges of designing a mission that includes both Enceladus and Titan as options. He didn't say too much that wasn't already in the mission proposal. He did say that the current mission configuration is subject to significant change should it be chosen.
I talked with another mission designer who thinks there may be options to first orbit Titan and then move to orbit Enceladus using relatively little fuel. He hasn't published his work, so I won't say more.
I stopped by the NASA booth at the conference. After trying to figure out how to “borrow” the detailed models of the Cassini and Phoenix spacecraft, I talked with the gentlemen at the radioisotope power table. This is the group that provides the radioisotope thermal generators (RTGs) for outer planet missions (including the MMRTG that will power the Mars Science Lab and the ASRG that reduces the use of plutonium dramatically). Right now, the generators are pretty big and sized to deliver hundreds of watts. They were polling attendees for mission ideas for power sources in the 10 to 50 watt range. Right now, mission designers have a choice of batteries, solar power, or large RTGs. If you want to do a mission with small probes where the probe has to operate for longer than batteries will suffice and solar power is difficult to impossible, then you are out of luck. If these small plutonium power generators were developed, they likely could enable a range of missions, such as network stations on Mars or Titan, long lived comet landers, long lived Venus balloons, small balloons carrying only cameras for Titan (think of four balloons instead of one imaging the surface), etc. These are only my ideas – the scientific community would come up with far more and more clever uses.
I'll write a separate blog entry or more likely a series to discuss the Venus Flagship proposal. One of the goals would be to fly a synthetic aperture radar that could image the surface at less than 10 m (6 m was mentioned). Only a portion of the planet could be imaged. However, I once read that each doubling of resolution increased the scientific content of an image by 10X. If I remember correctly, Magellan mapped Venus at a resolution of a hundred to hundreds of meters. This mission would do for our understanding of Venus what the high resolution cameras of the last decade did for our understanding of Mars. And those cameras imaged only a few percent at highest resolution.
Tuesday, December 16, 2008
Previous posts discussed general goals and constraints on a mission to Io and the science goals for such a mission. This entry discusses a specific mission concept, the Io Volcano Observer (IVO). Also see Jason Perry's write up on IVO.
NASA is facing a shortage of plutonium to use as a power source for future missions to the outer solar system (and other destinations with limited sunlight). A new design called the Advanced Stirling Radioisotope Generator (ASRG) would dramatically reduce the amount of plutonium required for future missions. The techology is new, however, and NASA may want to fly it first on an inexpensive Discovery-class ($450M) mission instead of on a more expensive New Frontiers ($650M) or Flagship (~$3B) mission.
Approximately a year ago, NASA began funding several studies of Discovery class missions that would provide a first use of ASRG's. One of those studies, led by Alfred McEwen of the University of Arizona, is for a Io Volcano Observer (IVO). Dr. McEwen was kind enough to provide me a copy of a presentation on the mission concept that he presented to the Berkeley Io Workshop on December 12. (The images come from his presentation.)
IVO would orbiter Jupiter in a highly inclined (>45 degrees) orbit with periapsis at Io's orbit. This orbit minimizes the craft's exposure to the intense radiation fields of Jupiter. On the other hand, it keeps the craft well away from Jupiter's other large moons. While significant obserations of Jupiter itself would be made, the focus of the mission is squarely on Io. Fans of other Jovian moons would be left waiting for other missions. (However, it is possible that IVO might be able to image some of the small moons that orbit inside Io's orbit. In addition, some long term observations of Europas extended atmosphere might also be possible.)
Red orbits are IVO's; white orbits are the major Galilean moons. IVO will not come close enough to Europa, Ganymede, or Callisto for detailed imaging, although studies of Europa's tenuous atmosphere may be possible.
McEwen points out that even if the Jupiter-Europa Orbiter (JEO) is selected as the next Flagship mission that IVO would still provide important complimentary science. JEO would provide 4 science flybys of Io before moving to targets further out in the Jovian system. IVO, however, would provide "unique polar viewing and in-situ sampling geometry of Io, torus, etc; spectral bandpasses designed for Io science, orbit designed to answer key Io questions, and the more flybys the better as Io always changes." IVO would also reach Io a number of years before JEO.
Most of the rest of this blog entry focuses on the nuts and bolts of the proposal, but I'll add my thoughts here. I am extremely impressed with the capabilities of this proposed mission, especially given the target budget of $450M (which it isn't quite hitting yet but is within striking distance). However, coming within striking distance may be enabled by the assumption (provided as a baseline for the concept study) that NASA would provide the ASRG's outside of the mission budget cap. Put another way, if the mission had to pay for its own power source (ASRG or solar cell), it might not be able to fit within a Discovery mission budget. NASA has yet to decide if it will do so for the next Discovery competition. I hope that McEwen or others will also propose a similar mission (using solar cells) for the New Frontiers competition in progress. The New Frontiers program would appear to have sufficient budget to fly the mission and include some additional instruments beyond the baseline planned for IVO.
[A note on mission classes: The price caps for each Discovery and New Frontiers mission are set with each selection competition. For Discovery missions, a working figure for mission costs is $350-450M for the spacecraft, instruments, and launch vehicle (plus other costs). For the next New Frontiers mission, the cap is $650M not including the launch vehicle. While exact comparisons are difficult, as a rule of thumb, Discovery missions appear to spend approximately half as much on spacecraft and instruments as New Frontiers missions.]
McEwen's e-mails to me suggest that he will not propose the mission as a New Frontiers candidate because the high data bandwidth needed to study the Io requires the power levels of the ASRG's. He also says that there are other issues with solar power. He didn't elaborate, but radiation damage to the solar cells and the difficulty of point the instruments at Io while keeping large solar panels toward the sun may be among them.
I would very much like to see a mission like this fly, whether within the Dicovery or New Frontiers program. (Although if Europa/Jupiter is picked as the next target for a Flagship mission, it would perform much of the science proposed for this mission.)
Here's a summary of key facts about the proposed mission:
"Primary science objectives:
1. Understand active volcanic processes on Io
2. Understand tidal heating of Io
3. Understand the loss of matrial from Io and effects on the magnetosphere, plasma torus and neutral clouds"
Launch in January 2015 on a Venus-Earth-Earth gravity assist trajectory with arrival at Jupiter in 2021.
Baseline mission has an Io flyby at orbit insertion, and six additional flybys over approximately a year and a half. Additional flybys in an extended mission are possible (>4 mentioned in the presentation).
Flyby distances range from 100-1000 km.
It appears that approximately 20Gbits of data would be sent to Earth per month. (Compare this with 0.2Gbits of data returned by the Galileo mission for Io.) Early in the mission, when orbit periods are longer, it appears that this data would be a mixture of Io and Jupiter observations. Later in the missions when the orbits are approximaly one month long, Io observations would dominate the available bandwidth.
Mission ends with impact on Io for planetary protection. (Keeps the spacecraft from accidently delivering Earth organisms to Europa.)
Total costs are currently conservatively estimated at $471M (including launch vehicle) versus a cap for the exercise of $450M. (No indication of how risky the mission implementation is within this budget compared to other Discovery program mission proposals.)
The baseline instrument complement focuses on the essential science (and weighs just 32 kg):
Narrow angle radiation-hardened camera with both a black and white framing mode and filters for pushbroom imaging in multiple colors that can provide 1 km/pixel resolution at 100,000 km or 10 m/pixel at 1,000 km. Science goals: monitor eruptions, measure peak lava temperatures, limited topography, Io surface composition (if budget allows for sufficient spectral filters), observe Jupiter's cloud deck (Tech specs: 10 urad/pixel compared to 5 urad/pixel for the New Horizon's LORRI camera; 2000 x 2000 pixel array with up to 1000 lines dedicated to multispectral imaging in pusbroom mode; spectral range ~200-1000 nm; up to 15 spectral filters; ~15 kg)
Thermal mapper to "map and monitor temperatures, heat flow pattern related to internal structure and tidal heating mechanisms." If budgets permit, the instrument could be enhanced to study Io surface composition using thermal emission spectroscopy and map Jovian hot spots. (Tech specs for this instrument appear to stil be in definition. Possibilities listed in the presentation are 640x480 detectors; ~2-20 microns; 1 km/pixel from 8,000 km; up to 10 bandpasses; ~12 kg).
Ion and neutral mass spectrometer to study spatial distribution of neutrals contributing to Io plasma torus , gas composition of Io plumes, composition of Io's (very thin!) atmosphere. (Tech specs: 1-300 amu; measurements every 5 seconds; 4 kg).
Magnetometer to study Jupiter's magnetosphere and "place tighter constraints on Io's internally generated magnetosphere (hard)" (Tech specs: 2 at 1 kg each)
This payload focuses on the essential Io science. Additional desired instruments in apparent order of priority are: more spectral bandpasses on camera and thermal imager; second, medium gain antenna to enhance gravity science; second neutral mass spectrometer with a different view; wide angle camera for better Io imaging close up, especially stereo imaging of topography; near-infrared spectrometer for minerology studies [my note: would also be useful for Jupiter observations]; UV spectrometer (s) for torus studies and Io atmosphere/plume composition.; energetic partical detector for "science and future exploration."
This evening I'll post a description of the proposed Io Volcano Observer. Later in the week, I'll post my thoughts on a Titan/Enceladus mission after seeing the presentations on those two worlds at the American Geophysical Union. I'll also post information on the proposed Venus Flagship mission.
In the meantime, be sure to check out Emily Lakdawalla's posts on results presented at the meeting. She does an awesome job of reporting on the the findings that a presented in fast moving meetings.
Monday, December 15, 2008
Tidal heating, a process that can greatly expand the habitable zones in the solar system and elsewhere, is best studied at Io because it provides the most extreme example of this process in the solar system. Io provides the best place in the solar system, beyond Earth, to study volcanism, a process of fundamental importance on many planetary bodies. Io also provides some of the most dramatic, freshest, and easily-studied examples of fundamental geological processes such as mountain-building and mass wasting. The volcanic activity on Io drives interlocking processes on a variety of time scales. While resurfacing/recycling the surface, the activity also provides volatile contributions to the Jovian sulfur and sodium nebulae via a time-varying atmosphere and exosphere. By providing approximately 1 ton per second of material deep within the magnetosphere of Jupiter, Io is a primary driver for most magnetospheric activity. With transport of material to Europa and the rest of the system, reenergization processes, and the Alfvénic interaction between Io and the upper atmosphere of Jupiter itself, scientists know that multiple, nonlinear feedback processes are present on many spatial and temporal scales.
An Io Observer mission should address some of the following science objectives, which are not listed in order of priority:
• Determine the magnitude, spatial distribution, temporal variability, and dissipation mechanisms of Io’s tidal heating;
• Determine Io’s interior structure, e.g., does it have a magma ocean;
• Determine whether Io has a magnetic field;
• Understand the eruption mechanisms for Io’s lavas and plumes and their implications for volcanic processes on Earth, especially early in Earth’s history when its heat flow
was similar to Io’s, and elsewhere in the solar system;
• Investigate the processes that form Io’s mountains and the implications for tectonics under high-heat-flow conditions that may have existed early in the history of other
• Understand Io’s surface chemistry, volatile and silicate, and derive magma compositions (and ranges thereof), crustal and mantle compositions and implications
for the extent of differentiation, and contributions to the atmosphere, magnetosphere, and torus; and
• Understand the composition, structure, and thermal structure of Io’s atmosphere and ionosphere, the dominant mechanisms of mass loss, and the connection to Io’s
It is likely that there are more objectives here than can be included in a single New Frontiers mission; proposals must state the science goals for the proposed investigation
and provide a rationale for the choice of science objectives. Any mission architecture that achieves the majority of the science objectives stated above for Frontiers cost cap will be considered responsive to this AO.
Sunday, December 14, 2008
Topics will be (1) Background on options for a return to Io, (2) science goals for an Io mission, (3) the proposed Io Volcano Observer, and (4) ideas for extended missions. This entry addresses the first topic, and entries later this week will address the other topics.
On a side note, I'm writing this while traveling to the American Geophysics Union (AGU) fall conference. While this conference is usually jam packed with results from missions in progress (and it will be again this time), this meeting will also have two sessions devoted to future Venus missions as well as poster presentations on several other proposed missions. It will take me awhile to work through the riches, but I will report on all the sessions over the next few weeks.
Background on options for a return to Io
A return to study Io has been a goal of a subset of the planetary science community (and based on our poll, the public that follows planetary exploration) ever since the end of the Galileo mission. While the Galileo spacecraft made several close flybys of Io, relatively little scientific data was returned in part because of the malfunctioning main antenna and in part because the intense radiation near Io caused the spacecraft to repeatedly go into safe mode just prior to closest approach. I don't want to downplay the value of the data returned. It was scientifically invaluable. However, only small portions of the moon were imaged and temporal coverage of this very dynamic moon was limited. One presentation I saw stated that just 0.2Gbytes of data were returned. That represented a very tiny window of data for what is a very dynamic moon.
The planetary science community has made a return to Io a priority. It is one of a handful of missions listed a priority targets for the next New Frontiers mission ($650M). (For a list of all the targets, see the previously mentioned poll.) Why is Io a priority?
o Because of extreme tidal heating, Io is the most active volcanic body in the solar system. The style of volcanism is believed to resemble that of the terrestrial planets in their extreme youth.
o Io is the best place to study tidal heating, a phenomenon that maintains a liquid ocean beneath the crust of Europa and possibly Enceladus.
o Io is a geologist's dream with interesting surface chemistry, grand mountains....
o Io is intimately connected to the Jovian magnetosphere and has even been called the heartbeat of the magnetosphere.
Currently, there are three possible routes for a return to Io. The most likely (in that there's a 50-50 chance the mission will be selected to fly) is the next Flagship mission (~$3B). (Titan is the other candidate target in this selection, which will occur in the next few months.) If Jupiter is the target of the next outer planets Flagship mission, it will include three close flybys of Io for science, including one pass that would go through (presumably the outer fringe) of a volcanic plume. (On Jupiter orbiter insertion, a flyby would also be done to use an Io gravity assist to reduce speed, but scientific observations apparently would not be done, at least with the remote sensing instruments.) Following the Io flybys, continued long range observations would be made for the remainder of the mission. If this mission flies, I doubt that any of the other possible missions that would target Io would be selected.
Let’s assume here, however, that Titan is chosen for the flagship mission. In that case, a New Frontiers mission to Jupiter would still be in the running. (The decision on the New Frontier's target will come in a couple of years.) Return missions have been studied for at least the past decade. I have a paper copy of a proposed Jupiter orbiter/multiple Io flyby Discovery program mission from about ten years ago. I believe that Io missions have been proposed for the Discovery program at least once and if not multiple times. None have ever become finalists.
If the mission(s) were proposed, two factors probably kept them out of the running. First, a $300-450M (budget caps have increased over time) budget is very tight for an outer planets mission. Both the New Horizons Pluto flyby craft and the Juno Jovian orbiter required the approximately doubled budget cap of the New Frontiers mission. In addition, radioactive power sources have not been allowed for Discovery missions. Solar cells can be used at Jupiter (the Juno Jupiter mission will use them, for example.) However, the intense radiation fields in the inner Jovian system where Io lies will gradually degrade performance of the solar cells, limiting the number of close passes. I've not seen a definitive answer as to how much, although at least a couple of studies have suggested that even the Europa orbiter mission (which would face much higher high radiation levels) could be done with solar cells.
Whatever its power source, an Io mission would orbit Jupiter and conduct multiple flybys of Io. The radiation field at Io is so strong that an Io orbiter's lifetime would be measured in hours to days – assuming the craft survived the radiation to even enter orbit. The total number of flybys would ultimately be limited by the cumulative radiation damage to the craft's electronics or (if used) solar cells. The craft can be designed to tolerate high levels of radiation exposure. An Io mission with the same radiation hardening as the proposed Europa flagship mission could do 50 – 100 flybys of Io within its radiation tolerance. (Note that this number is an extrapolation from a couple of presentations with different assumptions about radiation hardening; if any readers have better information, please pass it along.)
An Io mission study group that provided input to the 2003 Decadal Study proposed an Io mission that would encounter Io multiple times (up to 50) at the same place in its orbit. This way, lighting conditions would remain identical with each encounter. Different lighting conditions can make it difficult to determine whether apparent surface changes at Io are the result of true changes in the surface material or changes in lighting.
The Decadal Survey mission concept assumed a very capable craft with a radiation tolerance half that of the then proposed Europa mission. I don't know what degree of radiation hardening can be purchased within the $650M New Frontiers budget, but it is likely less. Radiation is a major design driver for the Juno Jupiter orbiter, which uses a “hole” in the radiation belt near Jupiter to minimize radiation exposure. I suspect that providing radiation hardening to the level of a Flagship mission is probably outside the budget of a New Frontiers mission.
On the other hand, we know that the New Frontiers budget cap is large enough to implement a mission to the outer solar system. Both the New Horizon Pluto and the Juno Jupiter missions are New Frontier missions. It is a reasonable guess that a robust Io mission could also be implemented within the budget cap.
In in the third part of this series, I'll report on a proposal to implement an Io mission within the much tighter Discovery mission budget.
Thursday, December 11, 2008
"The extra money, says NASA science chief Edward Weiler, will come from other projects involving Mars and possibly other planets. The queue contains three spacecraft to be launched in 2011--a small atmospheric probe to Mars, a robot to survey Jupiter, and a mission to chart the moon's interior. A 2016 Mars mission that has not been fleshed out will cost $800 million to $1.4 billion. And next month, NASA is expected to select a $3 billion spacecraft to study a moon of either Jupiter or Saturn that would be launched by 2020. "There will be impacts," says Weiler. "We probably will have to delay a major planetary mission.""
On possible cooperation between NASA and ESA on a 2016 Mars rover: "David Southwood, ESA's director of science, is reluctant to discuss NASA's possible contributions to ESA's ExoMars mission, proposed for 2016, before joint technical discussions are held early next year. He says that "some things are at the heart of the European investment," noting that ESA wants to test its mettle at landing on Mars and roving across its surface. But providing an orbiter to aid communication with Earth or instruments for the lander are areas in which NASA might be able to help, he adds. Cooperation would also be vital for any sample-return mission. This collaboration "is lifting a curtain on the future," Southwood says."
Wednesday, December 10, 2008
Nature's (one of the two leading science journals in English) lead editorial this week was on future Mars exploration. Some highlights:
"Future missions to the red planet require coordination — and a keen eye on costs.
"What this [past] huge investment [in one of a kind missions] has not produced, however, is the long-term infrastructure and reusable technology that would make future missions more affordable. To take one example: the most difficult part of any mission to the Martian surface is landing, yet every such mission to date has used technology tailored from scratch. There are currently no plans to reuse the rocket landing system painstakingly developed for Phoenix mission, nor the air bags of the rover missions, nor even the ambitious 'sky crane' system that will supposedly lower MSL to the surface from a kind of rocket-powered hovercraft.
"This constant reinvention is an indulgence that planetary exploration programmes can no longer afford... Rather than developing a new parachute-braking system, for example, the ExoMars rover being planned by the European Space Agency (ESA) could commit to using the air-bag technology deployed by NASA's rovers, and use as many of the other components from those missions as possible.
"Meanwhile, the most effective way to improve the returns on Mars exploration would be better cost discipline... Cancelling, or radically downscaling, overbudget missions such as MSL would set science back in the short term... But the only way to make Mars exploration a more regular affair is to stop the missions from costing too much. Eventually, a virtuous circle could be established: cheaper missions would mean more of them, which would mean less pressure to overload each one, in turn keeping the costs down."
Monday, December 8, 2008
In the United States, the President proposes a budget, but the Congress actually appropriates the money. (There's also a step, not done in all years of Congress authorizing a budget that is usually different than both the President's request and the final appropriation. Basically, the authorization is meaningless legally and financially but it allows politicians to show their support for programs without having to give them any money.) The President's budget proposal is delivered every year in late January or early February. Congress is supposed to then appropriate money by the start of the next fiscal year (FY) on October 1. Budget disagreements in recent years, however, have been so great that for many programs Congress has simply passed a continuing resolution that says the program will be funded at the previous year's level. NASA currently is operating on such a resolution, which has kept FY09 spending on the planetary program at FY08's $1,158M level instead of the President's proposed $1,330M level. This represents a funding cut of 13% below what NASA expected to carry out its planetary program.
In a possibly unique move, Congress has said that it will revisit the appropriation for all government agencies operating under a continuing resolution next March once the new President has made his priorities clear. The budget for the planetary program could remain at FY08 levels, go up, or go down. (My guess is that there would be little change. NASA is small potatoes compared to the rest of the budget.)
All of this makes it crazy hard I'm sure for NASA's managers to operate in in normal years, and even more so now that they know they have to make room for an additional $400M in MSL funding in the next two fiscal years.
Here is how NASA had planned its future spending last winter based on the President's proposal. This is from a presentation by James Green last March to OPAG. My apologies that the slide is clipped; it is that way in the posted presentation.
Eyeballing the chart, it appears that the funding wedge planned for the Mars program in FY10 and FY11 would almost cover the additional funds needed by MSL. After this chart was presented, NASA decided to push out the development of the next outer planet flagship mission, which (again by eyeballing the chart) partially covers the funding loss caused by operating under a continuing resolution instead of a larger appropriated budget. Taking funds from either the Juno or GRAIL missions looks like it could be counter productive. It looks like both enter their full development this year. If their launch is delayed, the development teams need to be kept together, potentially increasing their cost dramatically. (The time to delay a mission is before the peak funding and staffing occurs. )
These funding wedge charts may seem boring, but they are at the core of future mission planning. An agency has x dollars or euros (or name your favorite currency) to plan to spend for each year and the mission development and operations occur over a span of many years. What makes these charts so dynamic is that the funds expected to be available change yearly (in the U.S.; ESA has multi-year budgets and I don't know about other agencies) and the funds needed by missions change as they develop (for example, MSL's cost overrun). An agency can only commit to a new mission when a funding wedge becomes available and sometimes must cancel a mission when a funding wedge disappears.
Saturday, December 6, 2008
NASA has stated that it will first look for the additional money in the Mars program and then in the planetary program (and presumably after that, the rest of the science program). The manned program is under severe budget pressure as it is, and I don't see how it can be a source of funds.
If I remember correctly, NASA is currently operating under a continuing resolution that funds it at 2008 levels. A supplemental funding bill for the entire government is expected next spring to reflect the new President's priorities. If such a bill occurs, it could provide part of the additional funds required. President elect Obama stated in his campaign that he favored providing NASA with an additional $2B, although with the implication that it was to cover funding shortfalls in the manned spaceflight program. It's also unclear whether that was to be a one time or annual increase. The current economic problems and other budget priorities make me skeptical that this will happen. The rest of this entry is written with the assumption that the MSL budget hit will not be solved by the Congressional cavalry coming to the rescue.
I did bring along a slide from a presentation to the last Planetary Science subcommittee meeting (in October, I believe). It lists the following budget percentages for the planetary program for fiscal year 2009 (the Mars program is not broken out separately); no total dollar figure is provided. All number I believe referred to funding before the MSL schedule slip required shifting amounts:
MSL – 17%
Juno Jovian orbiter (2011 launch): 20%
GRAIL lunar orbiter (2011 launch): 12%
ExoMars and Mars Scout 2013 (the MAVEN orbiter): 2%
Funding for ongoing missions: 25%
I'm sure that NASA will squeeze the research and ongoing mission funding, but these programs tend to be hard to squeeze too much from. The research budget funds things like salaries for scientists. If you don't fund scientists, they tend to leave the field and are not available in the future. Ongoing mission funding can be reduced by either reducing the complexity of operations (anyone like to reduce the number of Titan flybys that collect science in the next two years?) or by shutting off working spacecraft (anyone want to propose that it is time to turn off Spirit?). So, some money is likely to come from these sources but not much.
Notice that the two Mars missions after MSL (ExoMars and MAVEN) account for very little of the budget (2%). Missions normally are developed over approximately four year periods and the large funding amounts come in the last two years. So MSL will launch before either of these missions are likely to become big pools of funding.
That leaves Juno and GRAIL as the only large pools of money left in the planetary budget. I would not be surprised to see either or both these missions delayed (but cancellation is unlikely). The funding to continue their development after their currently planned launch dates may come from ExoMars and/or MAVEN.
All of this is a thought exercise meant to show the complexity of the problem of finding the money for the MSL slip. (Also see an article on this topic at Space News.) In reality, the entirety of the NASA science budget and options for shifting funds around with some slips to some missions (for example, slip an Earth observing mission six months so that MSL can make its every 26 month launch window) are mind boggling. NASA has extremely dedicated and creative managers who will find the way to optimize (that is, minimize) the pain felt across the entirety of the program.
Former NASA science head Alan Stern has criticized NASA for allowing the MSL program to become so large and in his words, mismanaged so that this problem occurred. The thoughts below are mine but come from some of what he has written on this issue.
Budget overruns are as old as large development programs. They appear to be the norm for government funded development, whether military or space across nations and eras. (I can tell you from my experience in private industry that they are common there, too). Management systems could be put into place to minimize their occurrence. Until that happens (I'm not holding my breath), cost overruns will continue.
In my mind, the real trade off is whether or not to undertake large, ambitious missions. Small missions can and do have cost overruns. They tend to be less ambitious, so the probability of large overruns is less. In addition, because they are inherently smaller programs, the impact of large overruns is smaller. It is much easier to absorb a 25% cost overrun on a $500M mission than a $1.5M mission. In addition, NASA puts a large emphasis on selecting missions in this category that are low risk while the entire purpose of large, ambitious missions is to tackle the hard to do but big payoff projects.
I do not want to see NASA stop doing large ambitious missions. However, the management change I would propose would be to establish a large mission budget line item, Only one of these flagship-scale missions will be in development at a time. As one mission completes, the development of the next mission can begin. If the current mission slips and/or goes over budget, the development of the next mission is delayed.
Smaller missions then would be funded out of a separate line item that would not be tapped to pay for overruns on large programs.
Implementing such a plan would be difficult. Often, overall costs could be reduced if the funding for an over budget large program could be increased by tapping other budget line items. These large programs also have a lot of visibility and organizational momentum. The natural tendency would be to protect these key large missions at the expense of smaller missions. However, I think that such an approach is more likely to succeed than one that tries to eliminate cost overruns. And, of course, any improvement in minimizing cost overruns makes the system work better no matter how the budget is divided between line items.
Friday, December 5, 2008
An early opportunity will come with ExoMars. Both NASA (vague goal) and ESA (definitive plans with ExoMars) want to put rovers on Mars in 2016. Neither has the budget to do the mission themselves with the capabilities they would like to have. This could be a golden opportunity to pool resources. One big win would be if NASA were to use a derivative of its MSL precision landing system. This would open up a lot of interesting sites that have small landing footprints.
From Aviation Week's website: "We would have liked to have launched in 2009, followed up with our Mars Scout in 2013, and then a 2016 mission," said Ed Weiler, associate administrator for science. "That's going to have to be relooked at. Maybe we'll still have a good 2016 mission because we do it in consort with the European Space Agency."
Saturday or Sunday I'll post a blog entry on the challenges of finding the funds for the delayed MSL lander.
Thursday, December 4, 2008
Wednesday, December 3, 2008
Nothing in the article about how the new budget impacts possible funding for an ESA contribution to a Jupiter or Titan mission.
For those who want to watch the briefing, go to: http://www.nasa.gov/ntv
If the mission slips with a budget hit of ~$300M, that will be a severe blow to NASA's science portfolio unless Congress provides more money in the 2009 budget. This would be the worst case scenario that Alan Stern has been worrying about.
My fingers are crossed, but a slip is better than flying a mission that can't be ready.
Tuesday, December 2, 2008
I encourage you to read the full letters, but for those who are too busy, here are highlights from each:
"Before Mr. Griffin’s tenure, there was a long history of low-ball estimates. Senators or representatives with local constituencies to please would not let a major center project be canceled no matter how bad the overruns... Management of complex, technical projects in the current Washington environment requires extraordinary technical and political skill, as well as the ability to pick battles you can win."
"Whether during design, production or operations, the lack of a sufficient budget forces capable, well-meaning and goal-oriented government and contractor personnel to cut corners. This, in turn, often elevates safety risk... [ensuring adequate funding] may mean forgoing certain missions altogether and delaying others until it is “their turn.” Trying to finance everything at once on the cheap is a recipe for both budget and safety problems."
"While NASA must strive to be fiscally prudent, it is inevitable that when you attempt to perform science no one has ever tried, you will run into technological hurdles that cannot be anticipated... If NASA wishes to remain at the forefront of the world’s technology, it has to be willing to accept a certain amount of risk."
"Scientists are optimistic about how much they can do, managers are eager to accept low cost projections, and contractors are inclined to submit the lowest bid that is at all believable. But Dr. Stern’s bitter tone makes it easy to forget how astonishingly successful these missions have been... NASA needs to reform its process for developing programs while retaining the imagination and innovation so crucial to the endeavor."
"Alan Stern’s argument that “NASA’s managers and masters must all make cost performance just as important as mission successes” is absurd... The space program’s greatest accomplishments, including Apollo, Viking, Voyager, Hubble and Cassini, ended up costing more than NASA thought they would going in. So did the Panama Canal, the transcontinental railroad and almost everything else this country has ever done that was hard to do."
Monday, December 1, 2008
You can read the entire piece at http://www.thespacereview.com/article/1262/1