NASA Sticks With Decision to Cancel GEMS

NASA astrophysics division director Paul Hertz said today that NASA will stick by its decision to terminate the Gravity and Extreme Magnetism Small (GEMS) Explorer mission despite an appeal from the GEMS team to reconsider.

Hertz spoke at a media teleconference today to answer questions about the GEMS decision.   He had told the National Research Council’s Committee on Astronomy and Astrophysics on Monday that GEMS did not pass its confirmation review to move from the formulation phase into the implementation phase.   NASA missions must pass through a series of “gates” — called Key Decision Points or KDPs — as they progress from concept through launch.  A project can be stopped or required to make changes at those KDPs.  

Confirmation review is KDP-C.  Hertz explained that an independent cost assessment of GEMS as part of the KDP-C process revealed that the mission would cost 20-30 percent more, at a 50 percent confidence level, than the $119 million cap (excluding launch). 

A 50 percent confidence level means that there is a 50-50 chance that the project could cost either more or less than the estimate, but space projects rarely cost less.

Costs increased, he said, because the technology took longer than expected to develop, pushing out the launch date.  NASA then made the “difficult decision” to terminate the mission.  GEMS is an x-ray telescope in the Small Explorer (SMEX) series whose purpose was to study the polarization of x-rays in the vicinity of black holes and neutron stars.   Hertz said that the GEMS team submitted additional data as part of its appeal process earlier this week, but after reviewing it, NASA “affirmed the decision to non-confirm them.” 

Strictly speaking GEMS was not “cancelled” since it had not entered its implementation phase.  It was “not confirmed” to proceed, but the result is the same.

NASA is about to launch another x-ray telescope in the SMEX series — the Nuclear Spectroscopic Telescope Array (NuSTAR).  While NuSTAR will not study polarized x-rays from these celestial sources, it will be able to accomplish related science objectives Hertz said.

X-rays do not penetrate Earth’s atmosphere, so the only way to study x-ray emissions in the universe is using space-based instruments.   NASA launched the Chandra x-ray telescope in 1999 as one of NASA’s four “great observatories.”  The other three are the Hubble Space Telescope (visible and near-infrared), Spitzer Space Telescope (infrared), and Compton Gamma Ray Observatory (deorbited in 2000 after 9 years of observations).   Chandra was just approved for additional years of operations — through 2016 — as part of NASA’s Senior Review process.

NASA is working with the Japan Aerospace Exploration Agency (JAXA) on the Astro-H mission, an X-ray telescope scheduled for launch by Japan next year.   However, there are no plans for a large observatory-class x-ray mission.  NASA’s next observatory-class mission is the James Webb Space Telescope that will study the universe in the infrared wavelengths.  The National Research Council’s 2010 Decadal Survey for astronomy and astrophysics chose another infrared mission — the Wide-Field InfraRed Survey Telescope (WFIRST) — as the next priority for a large space-based mission, beating out the International X-ray Observatory (IXO) and other contenders.  IXO was ranked fourth out of four high priority large missions in the Decadal Survey because of technical, cost and programmatic uncertainties.

Hertz said that NASA will continue to offer the smaller Explorer-class opportunities for the various types of space-based astrophysics research, including x-ray astronomy, through the coming decade.   The money that would have been spent on GEMS, in fact, will be reallocated to future Explorer-class astrophysics missions.