Status Report

Update on Mars Exploration Rover (MER) Landing Ellipse Sizes

By SpaceRef Editor

September 6, 2001

Filed under Jet Propulsion Laboratory, Mars 2003 Rovers, US

To: MER Project and Landing Site Steering Committee

From: M. Golombek and J. Grant, Chairs Landing Site Steering Committee

Re: MER Landing Sites Ellipse Sizes

The MER Project has adopted DeltaDOR tracking with 5 TCMs (Trajectory
Correction Maneuvers) and has preliminary ellipse sizes for the science
community to evaluate at the upcoming Landing Site Workshop September
17-18, 2001 in Ithaca, NY. The ellipses are still preliminary, but we
wanted to take this opportunity to notify the community of them now, with a
follow up in about a week. All of the ellipses are subject to change in
the future as the project continues to refine its tracking and EDL
scenarios, although subsequent changes are likely in the ±20 km length
range.

The latest ellipse sizes and azimuths for the top 6 sites are:

ellipse
Site length x width azimuth
(km) (deg)
MER-A

Isidis 118 x 15, 88

Hematite 112 x 16, 83

Gale 104 x 17, 81

Melas 100 x 17, 80

Eos 94 x 18, 77

Gusev 94 x 18, 76

———————————————————–
MER-B

Hematite 108 x 17, 87

Melas 97 x 18, 83

And note that for MER-B, a site at 10 N latitude is: 10N 137 x 15, 95

For all of the sites except Gusev and Eos, all of these ellipses are
smaller than the previous ellipse sizes that were based on 5 TCMs without
DeltaDOR. Science spokespersons should include new ellipses in their
presentations at the upcoming workshop. For nadir sites not included
above, attached below is a graph of ellipse length and azimuth versus
latitude that can be used to estimate ellipse size and orientation. All of
the top six sites remain viable, although the edges of the Gale ellipse
cannot avoid steep slopes.

In addition, we notified you of 9 potential new sites that appeared viable
with ellipses smaller than those above in an e-mail dated 8/24/01. All but
three of these sites (Crommelin crater, Magaritifer Valles/Basin, and SE
Melas Chasma) remain viable with the slightly larger ellipses reported
herein. We will add discussion of the remaining 6 sites (Isidis, 2
Elysium, Ares Vallis, Sinus Meridiani, and Highlands) to the workshop
agenda.

Graph of ellipse length and azimuth versus latitude for MER A and B.