NASA has made its choices, and TESS is not one of them. The Transiting Exoplanet Survey Satellite would have used six telescopes to observe the brightest stars in the sky, a remarkable 2.5 million of them, hoping to find more than 1,000 transiting planets ranging in size from Jupiter-mass down to rocky worlds like our own. An entrant in the agency’s Small Explorer program, TESS could have accelerated the time-frame for discovering another habitable world, assuming all went well.
Not that we don’t have Kepler at work on 100,000 distant stars, looking for transits that can give us some solid statistical knowledge of how often terrestrial (and other) planets occur. And, of course, the CoRoT mission is actively in the hunt. But TESS would have complemented both, looking at a wide variety of stars, many of which would have been M-dwarfs. Not long ago I referred to a Greg Laughlin post that noted a 98 percent probability that TESS would locate a potentially habitable transiting planet orbiting a red dwarf within 50 parsecs of the Earth.
Were that the case, the results could have been handed over to the James Webb Space Telescope, scheduled for launch near the end of the putative TESS mission, for further investigation. JWST, so the thinking goes, could then take a spectrum and tell us something about conditions in that planet’s atmosphere. Retrieving data from the atmospheres of such planets is crucial to astrobiology and we’ll get it done one day, but perhaps not as soon as we hoped.
Getting a mission into space is no easy matter in the best of times (see Alan Boss’ The Crowded Universe for vivid proof of this). Consider that the two Small Explorer (SMEX) finalists were chosen from an original 32 submitted in January of 2008. The SMEX missions are capped at $105 million each, excluding the launch vehicle. That cost would depend on the vehicle — the last time I looked, an Atlas V would command $130 million. We’re talking relatively small investment for a solid scientific return, even if that return doesn’t include exoplanetary results on this round.
One of the two proposals now to be developed into full missions is the Interface Region Imaging Spectrograph, which will use a solar telescope and spectrograph to look at the Sun’s chromosphere. The other is the Gravity and Extreme Magnetism SMEX mission, which will measure the polarization of X-rays emitted by neutron stars and stellar-mass black holes, as well as the massive black holes found at the centers of galaxies.
Given that one of NASA’s stated aims with the SMEX program is “…to raise public awareness of NASA’s space science missions through educational and public outreach activities” (see this news release), the agency may have missed an opportunity with TESS. We’re close to the detection, through radial velocity or transit studies, of a terrestrial planet around another star. That’s going to put the study of that planet’s atmosphere for life signs high on everyone’s agenda, including the public’s. From the PR perspective, TESS was a gold-plated winner.