Minutes from Mars Landing Site Steering Committee Meeting

Held March 13th, 2001, at Tommy’s Patio Restaurant in Houston, TX

Meeting began with business items at ~12:00 p.m. and was followed by lunch before being closed at ~1:15 p.m.

The following members of Steering Committee were in attendance: John Grant, Matt Golombek, Ken Tanaka, Dick Morris, Roger Phillips, George McGill, Mike Shepard, Tim Parker Also in attendance were Jim Garvin (NASA Mars Program Scientist), Cathy Weitz (NASA MER Program Scientist), and Trent Hare (USGS landing site web site manager). Input on relevant issues discussed was solicited prior to the meeting via e-mail from Steering Committee members not able to be in attendance.

Discussion opened with a review of the upcoming schedule for Mars Landing Site Selection activities. Updates on activities were presented at the recent 32^nd LPSC with an additional update to be given at the Geologic Mappers Meeting in Albuquerque in June 2001. A Steering Committee meeting is planned for Fall 2001 (Date TBD, likely to coincide with Athena Team Meting at Cornell) to review newly obtained MOC images and other supporting data for high priority landing sites. As outlined in the minutes from the 1/25/01 Steering Committee meeting, the Fall 2001 meeting will be a "hybrid" Steering Committee meeting with the community being represented largely by persons assigned to particular high priority sites identified at the Ames workshop. Additional web-based comment mechanisms will be established to enable members of the science community to post additional information related to review of the high priority sites. It was agreed that assigning one person to take the lead in evaluating the science potential of a particular site (e.g., the person proposing the site at the Ames meeting) was a good idea. This person would be encouraged to review the landing site in context of all supporting data and to coordinate with other interested persons who could assist in, or make alternate, presentations. The goal will be to reprioritize the high and medium priority sites on the basis of review of all supporting data (not just MOC) to evaluate whether surface properties and/or science potential warrant a site’s relative priority on the list. It was agreed that the fall 2001 Meeting should be followed by a second open workshop in the April/May 2002 time frame for the purpose of recommending the two MER 10° by 15° landing site regions. A third, open workshop is tentatively planned for Spring 2003 to narrow the selection to one or two sites (primary and potential back up) within each landing region.

At present, NASA Headquarters anticipates two reviews of the MER site selection process/outcomes. The first would follow the down selection to the two landing site regions or "boxes" in Spring, 2002. The second would follow the identification of primary and possible back up sites within each landing site "box" and would take place in Spring, 2003.

The bulk of the meeting was spent discussing the three agenda items distributed/described in the memo of 2/22/01 (attached below).

The first item in the 2/22 memo related to the difficulty of completing thermal modeling and testing of the spacecraft in the extremely low temperatures likely to characterize the low thermal inertia, high albedo sites. Moreover, it was noted that even if a test program for the spacecraft could be devised, there would be a significant impact to the science that could be accomplished at such cold temperature locations. As a result, the Project has asked the Steering Committee to endorse elimination of landing sites possessing thermal inertias <250 SI units with albedos >0.26 and <200 SI units with albedos >0.18, which yield atmospheric temperatures colder than -95C. The only high priority site this would affect is the Elysium Marte Vallis outflow site (EP49B). Additional nadir only sites of opportunity that would be eliminated from consideration are Apollinaris at roughly 9.5S, 190.2W, Durius Valles (EP56A), and the other Elysium site (EP74A). Folowing some limited discussion (which included the possible substitution of other Elysium sites for Marte Vallis — rejected for lack of evidence for flowing water), the Steering Committee unanimously supported this action.

The second item in the 2/22 memo focused on the targeting of high priority sites in the Hematite and Isidis regions by MOC during ROTOs. Because only one site can be targeted during any given orbit, decisions must be made regarding which ellipse to target first with MOC (e.g., in the Hematite Region there 5 ellipses were listed as high priority for either MER A or B). If one of the landers is sent to a high priority site in Valles Marineris or a crater lake, for example, then MER B would most likely be sent to Hematite due to the limited range of latitudes accessible by the two landers. As a result, MER B sites in the Hematite Region probably should be prioritized higher than MER A sites. Given this and the preference expressed at the Ames landing site workshop, the following prioritized list (from highest to lowest) was discussed and unanimously approved for the Hematite sites.

TM20B, TM21B, TM19B, TM10A, TM9A

Based on similar arguments for Isidis Planitia, the following was discussed and unanimously approved as the prioritized list for MOC targeting (from highest to lowest):

IP85A, IP98B

It was stressed during the meeting that the above serves only to prioritize the sites in these two regions for MOC targeting. This process should not be interpreted as eliminating the "lowered" priority Hematite and Isidis sites from consideration.

The third item in the 2/22 memo related to a proposal to slightly shift the high priority landing ellipses within Melas (to the west) and Gusev (to the east). This shift has been proposed on the basis of preliminary analysis of available MOC imagery which indicates: 1) the presence of extensive dunes, a high scarp, and high regional slope towards the eastern portion of the layered terrains in Melas; and 2) a relatively flat and featureless plain in the western portion of Gusev that transitions to a more deflated, but still relatively smooth surface to the east (and potential better suited for sampling). Composite images of the new, slightly shifted sites were reviewed and the Steering Committtee unanimously approved the proposal.

Other discussion focused on potential issues that may arise in the future. The first of these relates to potential problems fitting the MER landing ellipse within Gale crater. Although all agree that this is a very intriguing and high priority site, a portion of the current ellipse (approximately 20%) is above the landing elevation limits and includes sections of 1km+ high crater walls. It was also noted that TES and IRTM data for the Gale crater site suggests a less rocky surface, otherwise broadly similar to that at Pathfinder (i.e., moderate dust).

It was pointed out that while the selection of the two MER latitude/longitude landing "boxes" must be picked by Spring, 2002, the consideration of all locations within those boxes as final sites can continue until shortly before launch. It was noted that there may be a desire to add potential landing ellipses within the "boxes" after Spring 2002 and that it will be important to coordinate image coverage of the "boxes" with Phil Christensen, PI of THEMIS.

Next, Mike Shepard provided a summary of the work he is doing with Ray Arvidson and Frank Seelos on processing the MOLA pulse width information to identify surface properties of the high priority landing ellipses. They are interested in understanding how the Martian topography behaves relative to comparison to terrestrial surfaces (based on comparison with an extensive existing data base). To do this, work focuses on synthesizing fractal surfaces to see what landing site hazards may look like based upon the pulse width data. Histograms of pulse width frequency are being compared with predictions of relief from terrestrial analog surfaces. For the Hematite sites, TM21B is different from other sites (smoother at ~150 m scale, but rougher at lander scale hazards). With this exception, the other Hematite sites are all quite similar. Crater Gale is the smoothest of the sites examined to date and is similar to the Hematite sites. Gusev looks to be quite rough, whereas Melas looks suitable for landing. Mike stressed that the results are preliminary and it was noted that it might be useful to use the detrended MOLA data for the work.

Finally, Trent Hare demonstrated the MER 2003 GIS CD to the committee. Much of the CDs functionality currently exists on the AMES and USGS web sites, but the inclusion of the stand-alone GIS software, ArcView Data Publisher, gives the user access to high-level queries, fast data access, the ability to include their own data sets, customized printing, and figure generation (exported as image or postscript). The CD contains many global data sets but also targets the high priority landing site areas with several more detailed data sets. Example databases include; MDIM1, MDIM2 (local), MOLA Shaded relief (global and local), surface roughness, elevation and slope contours, Viking IRTM, MOC footprints, MOC narrow angle images (local), TES derived data sets, etc. An Ellipse generator has been added to the software and will allow the users to create a correctly sized and rotated error ellipse. The ellipse will also generate information for several layers and a one-page map report. To help ArcView and GIS novices, the CD also comes with an "Intro to ArcView GIS" help section. Software patches and new/updated data sets will be at http://webgis.wr.usgs.gov/mer. More statistical information can be added to the ellipse report when the original data sets can be acquired (not just images of the data sets).

The following is an update on two issues that have surfaced related to landing site selection that we would like to make you aware of and receive any comments you might have. In order to ensure the opportunity to incorporate your input and discuss any other issues that may arise, we have scheduled a Steering Committee Meeting during the upcoming LPSC in Houston. Plans are to convene over lunch on Tuesday, 3/13, at a venue to be determined (but that will be close to the meeting).

As was noted and discussed during the Ames landing site workshop, thermal modeling of the spacecraft has shown extreme difficulty in testing the spacecraft in the extremely low temperatures likely at low thermal inertia, high albedo sites. Simple atmospheric thermal modeling shows that sites with thermal inertias <250 SI units with albedos >0.26 and <200 SI units with albedos >0.18, yield atmospheric temperatures colder than -95C. The current thermal design is based on a minimum atmospheric temperature of -95C, which thermal modeling shows that certain external hardware is about 10C colder (105C). For the required 15C test margin, this requires thermal qualification testing to -120C, which is the limit of present test facilities. Testing at temperatures colder than this would likely impact the cost, schedule and success of the test program.

Even if a test program could be devised, there would be a significant impact to the science that could be accomplished at cold temperature locations. Thermal modeling shows that about 56 W-hr is required to keep the rover interior warm at these locations, which translates into about 4 hours less instrument usage or 0.5 hours less data downlink per Sol. In addition, for external equipment, heaters would have to be added that would require an additional 20 W-hr (as well as mass and complexity), for these colder sites. Sites that have low thermal inertia and high albedo are generally considered to be dusty. Excess dust could further reduce solar power and coat rocks and surface materials. If surfaces at the site are coated with dust, it will be much harder to distinguish different materials with the Mini-TES, thereby reducing the variety of materials that can be measured in situ with the APXS and Mossbauer spectrometer and reducing the potential science return at these sites. As a result, the project is unanimous in requesting and endorsing this change.

The impact on the landing sites under consideration is as follows. Of the highest priority sites identified at the landing site workshop, only the Elysium Marte Vallis outflow site (EP49B) would be eliminated. Additional nadir only sites of opportunity that would be eliminated are Apollinaris at roughly 9.5S, 190.2W, Durius Valles (EP56A), and the other Elysium site (EP74A). None of the other high priority or targets of opportunity sites would be affected.

Images released by MOC of the landing sites in the past month are considerable (about 60). Many of the landing site ellipses are already covered by multiple MOC image swaths and we can look forward to ongoing excellent MOC coverage of the landing sites. These images have been released to the community and are available at the USGS and Ames web sites.

Preliminary review of these images permits identification of potential landing hazards and interesting science targets and has warranted a slight shift in two of the high priority landing ellipses. In Gusev Crater, the ellipse has been shifted slightly to the east, whereas in Melas Chasma, the ellipse has been moved slightly to the west. The new ellipse centers are located at approximately 184.15W, 14.85S and 77.78W, 8.80S for the Gusev and Melas sites, resepectively (see attached images).

There are two high priority landing regions, however, where many ellipses are bunched together (Hematite and Isidis), and decisions must be made regarding which ellipse to target with MOC in any given orbit as only one can be imaged during any given ROTO. Hence, it is necessary to prioritize targets within these two areas.

For the Hematite Region there are 5 ellipses (see attached image ). If one of the landers is sent to a high priority site in Valles Marineris or a crater lake, for example, then MER B would most likely be sent to Hematite due to the limited range of latitudes accessible by the two landers. As a result, MER B sites in the Hematite Region probably should be prioritized higher than MER A sites. Given this and the preference expressed at the Ames landing site workshop, the following prioritized list (from highest to lowest) is suggested for the Hematite sites.

TM20B, TM21B, TM19B, TM10A, TM9A

Based on similar arguments for Isidis Planitia (see attached image), the following is a suggested prioritized list (from highest to lowest):

IP85A, IP98B

Because of the potential impact to the MER Project (due to the thermal issue) and MOC imaging of the landing sites (due to the need to target during ROTOs), we request your review and comment on these issues ASAP. Please review these requests and attached materials at your earliest convenience and provide any feedback via e-mail to both John and Matt. We will discuss these items further during the lunch meeting at LPSC.