If NASA’s managers hold to their schedule, we will learn sometime this
month what NASA’s next planetary mission will be. This will bring to a close a two-year process
that saw 27 teams of scientists and engineers propose missions for the agency’s
Discovery program followed by a winnowing of the field to five finalists. Out of the process should come the selection of
one (and if the gods smile, two) missions that will launch in the early 2020s
to study either Venus or the asteroids.
The Discovery program funds NASA’s low cost planetary missions (typically
$600-700 million for all costs) to allow for more frequent missions. Nine missions have
successfully flown through this program to solar system destinations as diverse
as Mercury, our moon, Mars, several comets, and several asteroids. (For those who note that the next mission
will be the 13th selection, one previous mission failed, another is the
Kepler telescope observing planets around other stars, and one is still in
development.)
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| The Discovery mission finalists. Text in red refers to advanced technologies different teams propose to fly. Credit: NASA |
In the first round of this competition, the agency’s managers evaluated
the proposals on how compelling their science would be and on their engineering
and cost feasibility. This led to the
selection of the five finalists:
The Deep
Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI)
mission would use an entry probe to measure the trace gases in that planet’s
atmosphere to study the evolution and current state of the planet including recent
volcanic activity. It would also image
the surface of one of the continent-sized highlands known as tesserae.
The Lucy
mission would perform flybys of several of the Trojan asteroids that share the
orbit of Jupiter. These compositionally
diverse bodies are believed to be remnants delivered to their current locations
from across the early outer solar system.
Exploring these worlds would help us better understand the range of
conditions and orbital dynamics of the early solar system.
The Near Earth Object Camera
(NEOCam) mission would use a space telescope to both discover new asteroids
(especially those with orbits near Earth’s) and characterize a multitude of
know asteroids. The results would be a
massive database that could be mined to explore the range of asteroid sizes,
compositions, and orbital dynamics to study these worlds as entire populations.
The Psyche
mission would orbit the asteroid of the same name, which is the largest
metallic world in the solar system. This
body may be the exposed remnant center of a protoplanet, in which case it is
our only opportunity to explore the core of a world directly. Or Psyche may be an asteroid that formed
close to the early sun before later being flung into the main asteroid belt.
The Venus
Emissivity, Radio Science, InSAR, Topography, and Spectroscopy mission
(VERITAS) mission would remap the surface of Venus using radar at much higher
resolution than the 1989 Magellan mission.
It would also conduct the first global mapping of the composition of the
surface.
(In
a previous post, I provided more detailed summaries of the goals of each of
these proposed missions.)
The teams proposing these finalists have had approximately a year to
refine their proposals. The evaluation
of the final proposals is reputed to be a tough, rigorous examination looking into
all the details for any flaws. Could all
the science goals be met? Are there in
flaws in the design or proposed testing procedures? Could the mission be implemented within
budget? Do all the key personnel
proposed for the mission have the experience to execute the tasks assigned to
them?
The final evaluations are delivered to NASA’s Associate Administrator
for Science, Thomas Zurbuchen, who will make the final decision on which
mission to fly. Assuming that more than
one proposal survives the technical evaluation wringer, he may include factors
such as his judgement of which scientific questions are more compelling or
which mission would best balance the overall planetary program (for example,
NASA hasn’t launched a mission to Venus since the late 1980s but has launched three
asteroid missions since then).
It is possible that Dr. Zurbuchen will announce two missions to
fly. When the list of finalist proposals
was announced, NASA stated that a second mission might be selected if more than
one passed the final review process and sufficient funding was expected in
future budgets. Choosing two missions
from a single competition would make it easier for NASA to meet its goal of four
to five Discovery launches per decade. (The
competitions are expensive and time consuming for both the planetary community
and NASA.) As recently as this summer,
the head of NASA’s planetary science division said that his goal was to make
the case for two selections, but statements by other NASA managers have sounded
more cautious.
At least two recent events weigh, in my opinion, against a second
selection. First the Discovery mission
in development, the Mars InSight geophysical station, experienced development
problems and will need an additional $154 million to prepare for launch. Much of that money may come from the Discovery
program’s budget, reducing funds available for future missions. Second, the new president elect is promising
both massive tax cuts and massive new spending on infrastructure. Affording that program may lead to severe budget
cuts elsewhere in the federal budget, including
at NASA. Budgetary caution may be
the smart move.
While NASA’s managers likely will have found it hard to select from a
field of excellent candidates, among space enthusiasts there may be a clear
favorite. For the past year, my blog site has posted a poll asking
readers to select their personal favorites.
VERITAS was the clear favorite (48% of votes) followed by Psyche (19%), DAVINCI
(14%), Lucy (9%), and NEOCAM (7%). (The
poll also asked for votes for a second mission, should one be selected, and the
results were similar.) I am surprised
that the votes are not more evenly distributed – all the proposals are scientifically
compelling. Psyche and Lucy, for
example, would be missions of exploration to never before visited classes of
worlds. This poll likely represents the
personal preferences of planetary exploration enthusiasts (although members of
the professional planetary exploration community also read the blog and may
have voted), and therefore probably don’t represent the evaluation weightings
that NASA’s managers will apply. (So
far, over a number of mission selections, my personal favorite proposals have
been selected perhaps about 25% of the time.)
In the next few weeks, we are likely to learn which of these proposals
will be NASA’s newest approved mission, or missions. Whichever one is chosen, it will add
significantly to our understanding of the solar system.
