Exoplanetary Circumstellar Environments and Disk Explorer

{{Short description|Planned space telescope}}

{{Outdated|date=February 2021}}

{{Infobox spaceflight

| name = Exoplanetary Circumstellar Environments and Disk Explorer

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| mission_type = Space observatory

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| website = {{url|http://soweb.as.arizona.edu/~gschneider/EXCEDE_OVERVIEW.html}}

| mission_duration = 3 years nominal (proposed)

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| orbit_reference = Geocentric

| orbit_regime = Sun Synchronous

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| orbit_semimajor = 2,000 km

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| orbit_apoapsis =

| orbit_inclination = 105°

| orbit_period = 127 min

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| apsis = gee

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| telescope_diameter = {{convert|70|cm|abbr=on}}

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| instruments = Imaging polarimeter

| programme = Explorers program

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}}

Exoplanetary Circumstellar Environments and Disk Explorer (EXCEDE) is a proposed space telescope for NASA's Explorer program to observe circumstellar protoplanetary and debris discs and study planet formation around nearby (within 100 parsecs) stars of spectral classes M to B. Had it been selected for development, it was proposed to launch in 2019.

The spacecraft concept proposed to use a 70 centimeter diameter telescope-mounted coronagraph called PIAA (Phase Induced Amplitude Apodized Coronagraph) to suppress starlight in order to be able to detect fainter radiation of circumstellar dust.{{Cite book|arxiv=1210.3005 |doi=10.1117/12.927188 |chapter=The EXoplanetary Circumstellar Environments and Disk Explorer (EXCEDE) |title=Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave |date=2012 |editor-last1=Clampin |editor-first1=Mark C. |last1=Guyon |first1=Olivier |last2=Schneider |first2=Glenn |last3=Belikov |first3=Ruslan |last4=Tenerelli |first4=Domenick J. |volume=8442 |pages=84421S |editor-first2=Giovanni G. |editor-first3=Howard A. |editor-first4=Jacobus M. |editor-last2=Fazio |editor-last3=MacEwen |editor-last4=Oschmann }} Characterizing constitution of such disks would provide clues for planetary formation (mostly in habitable zones), while already existing exoplanets can be detected through their interaction with dust disk. The project's Principal Investigator is Glenn Schneider.