MARS EXPLORATION ROVER LANDING SITE MEMORANDUM 

      December 21, 2000 

      To: Project and Landing Site Personnel 

      From: M. Golombek and T. Parker 

      Re: Project Grinch that Stole Christmas 

      
We have just finished plotting the new landing ellipses for the 30
sites that received endorsement from the science community. As per our
memo dated 12/20/00, the ellipses have grown larger and we wanted to
see the potential effect on the 30 high science priority sites
identified by the science community. Overall the effects are
significant and negatively impact potential high priority landing
sites. The basic problem is that the ellipses have grown to a size
where it is difficult or impossible to avoid obvious potential
hazards. A number of sites in the Hematite area are eliminated (TM21B,
TM22B, TM23B, TM11A), although other Hematite sites remain, including
the favored TM10A. A few sites in Valles Marineris and the outflow
region are eliminated (CP35B, VM44A, VM47A, VM48A), although others in
Valles Marineris remain. A number of crater lake sites can no longer
fit within the rims of the craters.  Most significant is the favored
Gale crater site (EP82B), but also crater: EP69A and Boeddicker Cr:
EP64A and the new site suggested at Apollinaris Chaos at 11.1S,
188.5W.

These results will need to be cycled through the project. It is not
clear if the ellipses might shrink some in the future, so it does not
seem wise to eliminate these sites. Once the project comments on this
we should have a better idea about how to handle this before and at
the workshop.


Attached is the updated ellipse information from the MER
project. Compared to our last major mapping of the planet the ellipses
are generally larger with slightly different orientations. Compared to
our last amendment in the second announcement for the workshop, the
orientations are about the same, but the ellipses are longer.

For MER-A at the opening of the launch period, the new data is 

      Lat. Az. Length 
      5 88 219 
      0 83 186 
      -5 79 150 
      -10 73 114 
      -15 66 77 

In our last mapping, Memo dated Sept. 27, we assumed 

      Lat. Az. Length 
      5 88 166 
      0 87 150 
      -5 85 125 
      -10 83 115 
      -15 81 86 


For MER-B at the opening of the launch period, the new data is 
      Lat. Az. Length 
      10 99 338 
      5 95 286 
      0 91 234 
      -5 86 182 
      -10 79 130 

In our last mapping, Memo dated Sept. 27, we assumed 

      Lat. Az. Length 
      10 88 275 
      5 83 180 
      0 79 148 
      -5 73 130 
      -10 XX XX 

These changes will generally decrease the number of sites in the
northern half of the MER-A latitude band and decrease the number of
MER-B ellipses. At first glance, these changes doe not seem to have
much affect on the short list of sites identified. We will look at
these specifically in the next day or so and do a complete remapping
of all of the sites before the second workshop.

Happy holidays.