Saturday, August 6, 2011

PriME/MASPEX and Updates

I'll cover the updates first.  Aviation Week and Space Technology (AWST) has had a series of good articles on planetary exploration and space science in the last two issues.  (Unfortunately, most require a subscription.)  Amy Svitak, formerly with Space News, now writes for AWST, and continues her excellent coverage of policy issues there.

In an article discussing issues with NASA and ESA joint missions across a breadth of disciplines, Svitak reports that, "ESA is considering modifying the proposed Ganymede orbiter to to incorporate some Europa science."  Presumably, this would be science gathered in a series of Europa flybys. (Source: NASA's money woes thwart joint science missions with ESA)

In another article, Svitak reports that ESA is considering downsizing or eliminating its technology demonstration lander from the joint ESA-NASA 2016 mission so that more funding can be applied to the 2018 joint rover mission.  (Source: Europe could downsize Mars 2016 mission)

In yet another article, (this time not by Svitak), AWST reports that the Russian Phobos-Grunt sample return mission that will be launched this year is on track.


Sometimes a good mission concept can enabled by a single instrument.  When NASA announced it's list of candidate missions for its next Discovery mission (, it also listed three missions that would be funded for technological development to enhance their ability to compete in future selections.  One of these was the PriME mission, "Primitive Material Explorer (PriME), which would use an advanced mass spectrometer to provide high precision measurements of the the composition of a comet using a new, advanced mass spectrometer.

First some background on mass spectrometers, which are workhorse instruments in many laboratories and on many spacecraft.  To over simplify what they do, mass spectrometers 'weigh' the chemical compounds found in a plasma or gas.  (The composition of solids and liquids can be measured by heating them until they vaporize.)  The weights of the different molecules form a mass spectra that can be interpreted to determine the compositon of the orginal material.

Two figures of merit are frequently quoted when comparing mass spectrometers.  One is the range of masses they can measure, which are frequently expressed in atomic mass units (amu), which are approximately the mass of a single proton or neutron.  The Cassini spacecraft's Ion and Neutral Mass Spectrometer (INMS) has a range of 1-99 amu, the Rosetta spacecraft has two mass spectrometers with ranges of 1-150 and 1-300 amu, and the Mars Science Laboratory's mass spectrometer has a range of 2-535 amu.  The second figure of merit is the resolution of the measurements in terms of how finely different masses can be distinguished.  (The websites for the different instruments either do not give the second figure or report it in different units.)

The PriME mission would fly a next generation space-borne mass spectrometer, MASPEX, with a range of 1-1000 amu.  MSPEX's resolution and sensitivity would allow far more precise measurements of the composition of the gases released by a comet that has been possible with previous and current missions.  MASPEX could help us work around a key limitation of any comet sample return launched this decade. We currently lack the technology to keep many of the cometary ices frozen throughout the long delivery back to Earth.  As a result, we'd lose the ability to measure pristine samples.  An instrument like MASPEX could enable more precise measurements at the comet of unaltered materials.  It's not clear, however, that MASPEX would be flown on a sample return mission itself.  A sample return mission is likely to sample the comet as far from the sun as possible to avoid its volatile outgassing and then head back as early as orbital mechanics allow.  A spacecraft carrying MASPEX, however, would want to linger at the comet through out the periods of maximum outgassing closest to the sun.  As a result, separate missions might be likely.

An enhanced mass spectrometer would be useful in missions to many types of destinations including Mars, Titan, and Enceladus.

We have no details on MASPEX's cost, mass, size, or power requirements compared to current generation mass spectrometers (which apparently can be among the heavier and more costly instruments for many missions).  Hopefully, MASPEX will be competitive, and will provide a new level of capability for a wide range of missions.  For some destinations, its improved capabilities would be enabling by itself, as with the PriME mission.

With the permission of the PriME mission's Principal Investigator, Dr. Anita Cochran, I'm reprinting an abstract on the PriME mission.  I'm also reprinting a press release on the MASPEX mass spectrometer.  I've read elsewhere that while this mission wasn't selected as a finalist for the current Discovery mission selection, the team plans to propose it again for the next selection.

The Primitive Material Explorer (PriME) Mission

Cochran, Anita L.; Weaver, H. A.; Science, PriME; Engineering Teams
American Astronomical Society, DPS meeting #42, #49.17; Bulletin of the American Astronomical Society, Vol. 42, p.1006
The Primitive Material Explorer (PriME) Mission is a proposed Discovery mission that will rendezvous with comet 46P/Wirtanen in 2021 in order to 1) clarify the roles played by comets in the formation and evolution of the Solar System and the origin of life; 2) ascertain the bulk physical properties, the surface geology, and the sources of activity in a fresh comet nucleus; and 3) investigate the compositional diversity of primitive material in the Solar System. PriME teams an experienced group of comet scientists (led by PI Anita Cochran and by DPI Harold Weaver) with university and industrial partners.

The PriME payload accomplishes the mission objectives with only three instruments. MASPEX (MAss Spectrometer for Planetary EXploration) has higher mass resolution and is more sensitive than any mass spectrometer ever flown. MASPEX will measure D/H in H2O, noble gases, isotopes of many species, and complex molecular compounds to test solar nebula models and the role comets played in delivering water and other biologically important materials throughout the Solar System. The VIS (Visible Imaging System), consisting of a Narrow Angle Camera (NAC) and Wide-Angle Camera (WAC), will constrain the conditions under which the building blocks of the outer Solar System were assembled by measuring key physical properties of the nucleus of 46P/Wirtanen. Using the radio antenna and close flybys of the nucleus, PriME will determine the mass of the nucleus to an accuracy of 1% and the bulk density and average porosity of the nucleus to better than 5%. All spacecraft subsystems have significant planetary flight heritage. The spacecraft is a high-heritage derivative of the Kepler and Deep Impact spacecrafts, compatible with the three launch vehicle families specified in the Discovery Announcement of Opportunity.

NASA selects SwRI mass spectrometer for technology development funding, possible future planetary mission

For immediate release

San Antonio — May 17, 2011 — NASA has selected Southwest Research Institute's MAss Spectrometer for Planetary EXploration (MASPEX) for technology development funding. Originally offered as part of the Primitive Material Explorer (PriME) mission proposal, the mass spectrometer was selected to further advance NASA's capability for evaluating the chemical composition of comets.

MASPEX is a highly sensitive ion and neutral mass spectrometer based on novel detection technologies under development by SwRI. Although similar to a spectrometer on the ESA Rosetta mission currently on course to reach comet 67P/Churyumov-Gerasimenko in 2014, MASPEX extends its resolution and sensitivity by one to two orders of magnitude. The spectrometer is designed to measure precisely the composition of volatile gases and plasmas found in planetary atmospheres as well as comets. Identification of isotopes in these extremely low-density populations is a particularly challenging target and an area where MASPEX is expected to excel. In addition to comets, the SwRI team is exploring a number of Earth-based spin-off applications of this novel technology.

Institute Scientist Dr. Hunter Waite and Program Director Dr. David Young, both of the SwRI Space Science and Engineering Division, serve as MASPEX co-principal investigators.

"With further development, MASPEX will have by far the highest sensitivity for identifying, measuring and sampling gases and plasmas of any mass spectrometer ever flown in space," says Waite.

"Measuring isotopic composition will yield for the first time quantitative clues to the origin of comets and other bodies in the solar system, and could provide valuable insights into the origin of life," Young adds.

To be considered for space flight, the SwRI team must demonstrate continued advancement of the technology in preparation for a future mission proposal. The spectrometer is one of three technology developments selected by NASA for further development.

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