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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. The spacecraft will 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. 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 Dr. Glenn Schneider.
Scientific goals 
- Explore the amount of dust in habitable zones
- Determining if such a disk interferes with future planet finding missions (dust-scattered starlight causes noise in images of exoplanets)
- Determine composition of material delivered to planets. Icy and organich-rich particles are important for life.
- Determine of fraction of massive planets on large orbits
- Observe how protoplanetary disks make Solar System-like architectures
- Constrain giant planets' composition by measuring their reflectivity EXCEDE will be the first to image (giant) exoplanets distances from their stars similar to ours (0.5-7 AU).