[X] My Assistant

[Cugel]

BigDog

Imagine this thing with a pancam on the front and a low gain antenna at the rear....
It's a Martian Lama!

[Simon_Frazier]

Hello all:

After years of lurking and reading all of your postings on a daily basis, I thought I'd join the forum and contribute where I am able as a non-technical armchair enthusiast.

The recent announcement that Opportunity may well be headed to Ithaca/Endeavour has reminded me of a topic that I have long wanted to get UMSF members' views on - one which doesn't appear to have been discused at any length before:

Do you think it would make sense for NASA to build a fleet (let's say between 4 and 8) of _slightly_-improved MER "Mark 2" rovers (or "MER 2.0" if you prefer), and send them off to Mars at a rate of 1 or 2 per opposition?

Here are my own top 3 reasons why NASA might want to commit to building a corps of "MER Mk.2 " rovers:

1. Familiarity: After more than 3000 sols of experience, including more than 20 km of driving, 100,000+ photos, 3x2 winters and 1x2 severe dust storms, the MER rovers have gone through a phenomenenal amount of road testing. In addition to this, there is also the 4.5 years of hands-experience with the test units at JPL. Perhaps of equal importance, there is also a large group of people with extensive direct experience in working with the MERs.

2. Performance: These rovers have turned out to be wonderfully well engineered (and operated). While Spirit is certainly showing its age, and Opportunity could suffer some sort of catstrophic fault in the near future, both of these rovers have now been producing useful science more than 18 times longer than their original intended mission. I think it would be reasonable - conservative, even - to expect a new MER built to _exactly_ the same design to travel at least 5 kilometers, and to survive at least 1 to 1.5 Martian years (i.e. until a second dust storm and/or winter season.)

This is not to say the rovers are perfect as is. They're not. But we now have a very good understanding of their limitations and design drawbacks. In fact, I think it's our deep understanding of the current MERs' imperfections that makes the idea of an incrementally-improved MER Mk.2 so attractive to my way of thinking - we have a very good idea of what really needs fixing. Moreover, it's my perception (as a non-engineer), that most or all of the crucial vulnerabilities in the design of the MER could be addressed with incremental changes to individal parts of the rover, rather than through a overall redesign.

3. Cost: This is the least certain of the advantages, but my assumption is that if 90% of a MER Mk.2 rover is identical to the MER units currently operating on Mars, then a lot of the neccessary modelling, designing and testing work (and expense) has already been done. And if building Opportunity as a second rover cost only half again as much as building Spirit alone, then I'm assuming there could be even greater per-rover cost savings from building 4, 6 or 8 MER Mk.2 rovers at once.

I'm very interested to know what you all think!

[djellison]

Do you think it would make sense for NASA to build a fleet (let's say between 4 and 8) of _slightly_-improved MER "Mark 2" rovers (or "MER 2.0" if you prefer), and send them off to Mars at a rate of 1 or 2 per opposition?

Two main reasons why not.

1) There are not that many safe places that are scientifically interesting to land MER style landers

2) Are you paying?


Doug

[Simon_Frazier]

Whups.

I see now that there WAS quite a discussion at the end of 2005 about sending a third MER to Mars here:


Mer 3 Possibility?


I wonder if people's conclusions from then still hold, or whether the continued survival (and scientific activity) of the rovers for a further three years has changed the cost-benefit equation appreciably?

Regarding your the first of your two responses, Doug, my understanding is that the list of potential sites back for Spirit and Opportunity were quite limited (Athabaska Vallis was the only other real contender, if I remember correctly). But I wonder whether a new call for potential sites might come up with a longer list of good candidates, if the capabilities of the MERs were redefined in terms of what the MERs have since shown themselves to be capable of. That is, rather than looking for sites appropriate for rovers that have a 90-sol lifetime and a 600-metre range, a new site selection process would be looking for sites appropriate for rovers with a ~1000 sol lifetime, and a 5-or-better km range.

[djellison]

But I wonder whether a new call for potential sites might come up with a longer list of good candidates,

I think HiRISE data would probably reduce the number of candidate landing sites. It's not about rover longevity. MER still can not be guarenteed to do a 'drive to' with a range of, say, 6km and an ellipse 10x that distance long. It's about safe, interesting landing sites - and for MER, there are not very many.

As Mike Caplinger has said several times, MER heritage is in the box level...the pieces of the machine. Navcam and Hazcam and going on MSL. Various other components might find use in other vehicles.

And even if we had 100 brilliant, safe landing sites for the MER design - the question still remains..

Who's paying?


Doug