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The problem with the purest form of this suggestion ("build two") is that Mars missions are missions of exploration, so you learn things, and then the next miss

The problem with the purest form of this suggestion ("build two") is that Mars missions are missions of exploration, so you learn things, and then the next mission needs different instruments. So you really don't want to build/test/integrate two. But, I think your comment is getting at something very important, which is to have a pipeline of missions that run in some orderly way, so that you can build on prior knowledge and success. Like the original Mars Pathfinder rover (1997) paving the way for Spirit/Opportunity (MER, 2004), and then Curiosity/MSL (2012) and next Mars 2020 (2020). These have shared a lot of components, and some prototype systems that started out as "experiments" on MER made their way into "production" in MSL - such as autonomous data-taking (http://www.planetary.org/blogs/guest-blogs/2018/0313-automating-science-on-mars.html http://www.planetary.org/blogs/guest-blogs/2018/0313-automat...), and computer vision to detect obstacles during descent (https://www-robotics.jpl.nasa.gov/projects/projectImage.cfm?Project=1&Image=65 https://www-robotics.jpl.nasa.gov/projects/projectImage.cfm?... -- this moldy old page is from MER, but the same idea was later used on MSL and slated for M2020). If you can set up this kind of pipeline, it's very powerful.

opportune 9y ago
Disagree with your first note, as rovers are only able to cover a very small area over their lifetimes and there could be a large benefit to exploring more locations in general (higher chance to discover new compounds/geology, able to explore more areas around caves and poles and learn interesting things). And of course for probes we could definitely benefit from having a dedicated orbiter for each body in the solar system, or even multiple if it let us e.g. build a GPS system for Mars.
- mturmon 9y ago
  We did build two for MER, but then went back to one for MSL and for the upcoming M2020. The community provided input for this, so it's not an arbitrary decision. The definitive guidance on scientific thinking behind these plans is MEPAG, see: https://mepag.jpl.nasa.gov/reports.cfm https://mepag.jpl.nasa.gov/reports.cfm. Besides its most recent report from 2015, it links to an older National Academies report (the 2013 Decadal Survey). Turning to page 160 of the (long!) Decadal Survey document (free!), we read: "The committee carefully considered the alternative of several rover missions instead of sample return [for Mars]. It is the opinion of the committee that sample return would have significantly higher science return and a much higher science-to-dollar ratio. [...] Existing scientific knowledge of Mars makes it possible to select a site from which to collect an excellent suite of rock and soil samples to address the life and habitability questions..." So, one way to reframe your objection is that we are in truth planning multi-mission coordinated observations, but in the context of sample-return. M2020 is going to select and store samples, and a subsequent mission is planned to return them. That's the kind of progression that seems to galvanize the science community. Aside: Besides the above reports, which (I hope) provide reassurance that all options are being considered, there's also the context of the site-selection process for M2020 - see https://marsnext.jpl.nasa.gov/index.cfm https://marsnext.jpl.nasa.gov/index.cfm. You might enjoy looking at the viewgraphs for the very last talk of the most recent (2017) workshop, which summarize some of the site considerations.

opportune 9y ago

Disagree with your first note, as rovers are only able to cover a very small area over their lifetimes and there could be a large benefit to exploring more locations in general (higher chance to discover new compounds/geology, able to explore more areas around caves and poles and learn interesting things). And of course for probes we could definitely benefit from having a dedicated orbiter for each body in the solar system, or even multiple if it let us e.g. build a GPS system for Mars.

mturmon 9y ago
We did build two for MER, but then went back to one for MSL and for the upcoming M2020. The community provided input for this, so it's not an arbitrary decision. The definitive guidance on scientific thinking behind these plans is MEPAG, see: https://mepag.jpl.nasa.gov/reports.cfm https://mepag.jpl.nasa.gov/reports.cfm. Besides its most recent report from 2015, it links to an older National Academies report (the 2013 Decadal Survey). Turning to page 160 of the (long!) Decadal Survey document (free!), we read: "The committee carefully considered the alternative of several rover missions instead of sample return [for Mars]. It is the opinion of the committee that sample return would have significantly higher science return and a much higher science-to-dollar ratio. [...] Existing scientific knowledge of Mars makes it possible to select a site from which to collect an excellent suite of rock and soil samples to address the life and habitability questions..." So, one way to reframe your objection is that we are in truth planning multi-mission coordinated observations, but in the context of sample-return. M2020 is going to select and store samples, and a subsequent mission is planned to return them. That's the kind of progression that seems to galvanize the science community. Aside: Besides the above reports, which (I hope) provide reassurance that all options are being considered, there's also the context of the site-selection process for M2020 - see https://marsnext.jpl.nasa.gov/index.cfm https://marsnext.jpl.nasa.gov/index.cfm. You might enjoy looking at the viewgraphs for the very last talk of the most recent (2017) workshop, which summarize some of the site considerations.