Minutes from Mars Landing Site Steering Committee Meeting
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 32nd 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).
1.)
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.
2.)
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.
3.)
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/cd/. 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).