Monday, June 3, 2013


Last February, I wrote about proposals to use two surplus spy telescope assemblies for planetary science (Brother, Can You Spare $1B for a Planetary Space Telescope?).  Since then, one study team has completed a study on uses of one of the telescopes for astrophysics studies.  (Another team will report soon on the best proposals for possibly using the second telescope assembly.)  The proposal goes by the more formal Astrophysics Focused Telescope Assets (AFTA) or informally at WFIRST-2.4.  ('WFIRST' is the acronym for a proposed dark energy telescope and 2.4 refers to the 2.4 m mirror of the telescope.)

The primary goal for the astrophysics mission is to study key questions about the structure of the universe and the nature and role of dark energy and dark matter.  (Together, these invisible components make up the vast majority of the universe's mass.)  

However, the team also examined uses of the mission for exoplanet studies.  Here, the mission could conduct distinct surveys.  Using the same camera-spectrometer as the astrophysics study, the telescope would spend long periods staring towards the center of our galaxy.  The instrument would occasionally catch an exoplanet transiting in front of a background star.  The gravity of the planet would distort the image of the background star, revealing the mass of the planet.  Operating in this mode, the telescope would be expected to detect an estimated 3,000 or more planets.  Where the Kepler telescope specialized in detecting planets close to their stars, this mission would specialize in detecting planets further out (including those floating in space between stars).  

The study team also is proposing that the telescope be equipped with a coronagraph.  This instrument would use a shade to block the bright light of nearby stars, permitting direct imaging of Neptune and Jupiter-class planets.

Phil Horzempa has written an excellent summary of the exoplanet capabilities of this proposed mission at the Space Review (Exoplanet capabilities of WFIRST-2.4).  (Phil also has contributed to this blog.)  I encourage you to read his story.

In the meantime, here are a couple of slides from a summary presentation on the proposal to whet your appetite.  You can see the entire presentation here or read the study team's report here.

If the mission flies, it would be launched sometime in the early 2020s.  The team did not make its cost estimate available.  Later this month, NASA's administrator will decide whether or not NASA will continue to study this option.

One of the exciting capabilities of WFIRST 2.4 is that it would have a much wider view than the Hubble Space Telescope while retaining Hubble's resolution.  The following two images show how two WFIRST 2.4 images would cover the same area that would require 432 Hubble images.

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