The briefness of the requirements for the Trojan theme likely makes life harder for teams proposing a mission to these worlds. In judging proposals, NASA’s review teams will score proposals on their scientific merit (~40% of score), the feasibility of the specific proposed instruments and measurements (~30%), and overall mission feasibility within the cost cap (~30%). Scientific merit includes an explanation of the, “Compelling nature and scientific priority of the proposed investigation's science goals and objectives. This factor includes the clarity of the goals and objectives…” Teams proposing for Venus have the benefit of goals developed and specified by the Venus science community while teams proposing for the Trojans have to develop and defend their own list of specific science goals and objectives. (At the end of this post, I’ve copied the specific goals for the remaining mission themes from the AO.)

Missions proposed for the next New Frontiers program will need to meet many criteria including these:

Total cost for the development of the spacecraft, the instruments, and analysis of the returned data cannot exceed $850 million. NASA will separately pay for the mission’s launch and operation costs while in flight (likely several tens of millions of dollars per year), which together probably will bring the total cost of the mission to $1 billion or more.

Proposals can include instruments paid for by foreign governments, but the costs of these instruments cannot exceed one-third of the cost of the total instrument compliment. As one NASA manager put it, NASA invests a great deal of money to develop instrument technologies by American scientists, and it wants to see a return on that investment by having the majority of instruments on the selected mission be American.

Teams can propose the use of radioisotope heaters and radioisotope electrical power generators for their missions. These units would be useful for missions operating far from the sun (for example, at Saturn). However, a mission using these units would need to reserve a substantial portion of the core $850 million to cover the cost of these units. Using just the heaters would incur a cost of $47-79 million (depending on the number) and the electrical power generators would cost $133-195 million (again based on the number of generators used). These costs could drastically reduce the capabilities of the spacecraft and instruments compared to missions that don’t require these technologies.

I suspect that for many readers of this blog, a mission to return to Enceladus or Titan to continue their exploration with a new generation of spacecraft and instruments would be a personal favorite. I share that desire, but also recognize the challenges any proposal to these worlds would face. First, these worlds were just added to the list of candidate themes in the past few months. The in-depth analysis of objectives for these missions is just getting underway by the scientific community. Second, the technical maturity of instruments to explore their oceans, determine their habitability, and search for life may be low – NASA has not made major investments in these technologies for these worlds (but plans to begin to do so). And third, these missions are likely to need radioisotope power generators and their cost would eat significantly into the mission budget, potentially making it less competitive. (Solar powered missions are possible at Saturn, but appear to be on the edge technically. This could make a proposal that depends on solar power appear technically risky.) Balancing these negatives is a heritage of three Discovery-class proposals to these worlds that were not selected but which could form the basis of a New Frontiers-class mission. Still, I personally doubt that a mission to these moons will be selected this time. (If I am wrong, given a mid-2020’s launch and a flight that could last 10 years, it could be the mid-2030s before the spacecraft arrives at its target.)

I’ve learned to not try to predict which Discovery or New Frontiers mission is likely to be selected from the list of proposals made. The scrutiny given these proposals is intense. Any fault with the details of a proposal can rule it out. If the review panel decides that a proposed key engineering manager doesn’t have sufficient experience, that could kill a proposal. If the review panel concludes that a technology proposed to be used for the spacecraft or a key instrument lacks maturity, that could kill a proposal. If the review panel concludes that the specific set of scientific objectives proposed are not as compelling as for other proposals, that could kill a proposal. No matter how sexy a proposal might look from the limited information that we in the general public get to see, faults in the details that we never see may rule it out.

However, we need to remember that all the candidate themes for the upcoming selection of the fourth New Frontiers mission represent questions deemed to be among the highest priority for exploring the solar system. Whichever mission is finally selected will significantly expand our understanding of the solar system.

Schedule for the next New Frontiers competition and launch:

Final AO Release Date -- January 2017 (target)

Deadline for Receipt of Proposals -- AO Release + 3 months + 4 days

Selection of a subset (historically, two) of proposals for further study -- November 2017 (AO release + 10 months)

Final selection -- July 2019 (target)

Launch -- December 31, 2024 if solar powered or December 31, 2025 if radioisotope power sources are required

Flight time to the target world: Days (the moon), months (Venus), years to a decade or more (comet with Earth return, Saturn, or Trojan asteroids)

Science goals for the remaining mission themes (goals for the Venus and Trojan asteroid themes listed above):