This continues a series of posts inspired by a similar set of posts at Future Planetary Exploration blog selecting the 5 most compelling missions from the Planetary Science Decadal Survey list. This is the 2nd of 3 reviews of potential Mars missions, building up to a selection from that list (and I've already revealed that Mars will not be skipped in my selection of 5 compelling missions).
The Mars Geophysical Network Options Decadal Survey study presents a number of options beyond the Network Pathfinder described in the previous post to study the interior of Mars. The science to be addressed by these mission options includes seismology, precision tracking to measure Mars rotation rate, precession, nutation, and polar motion, meteorology to determine atmospheric effects to the seismology instrumentation, subsurface heat flow analysis, and electromagnetic sounding. Science goals including measuring the structure, composition, and size of the crust, mantle, and core, and measuring heat flow through the crust. For simplicity, only the key seismology and (telecommunications-based) precision tracking capabilities are considered in cost comparisons, although there is ample room for more instrumentation in the landing mass allowances. Because multiple simultaneous seismology measurements increase the value of these measurements considerably, from 1 to 3 distributed landers are considered in the options (hence the Geophysical Network). Other variations beyond the number of landers include landing method (airbag or powered), mission "class" (New Frontiers, Discovery, or Mission of Opportunity hitching a ride), and method to get to Mars (shared vehicle, free flyer, or secondary payload)
Interestingly, the basic "Mission of Opportunity" scenario estimated costs ranged from $522M to $627M, far higher than the Sky Crane Network Pathfinder option described in the previous post. New Frontiers class scenarios with 2-3 landers ranged from $1,015M to $1,347M; only the scenario with only 2 powered landers fit the New Frontiers cost limit. For the Discovery mission class options which all had only 1 lander, only the Falcon 9 launch and powered landing approached (but, at $720M, still exceeded) the anticipated FY15 Discovery mission cost limit. It is noted that for these missions with high heritage from systems already used on Mars (e.g.: Mars Phoenix, Mars Exploration Rovers, and Mars Pathfinder), the Decadal Survey's required development phase reserves (50%) might be more than is needed for these mission options with little technology to develop. Also, costs were made based on all U.S. development, but it's expected that the main instrument, the seismometer, would be contributed by a European agency. It's possible that additional instruments would use funding sources from outside NASA Planetary Science, too.