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Getting Started at MAST with EPOCh data

The EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) mission, as the name implies, was a follow-on mission of NASA's Deep Impact probe, which was launched as a Discovery class mission to study the interior composition of a comet. EPOXI is administered by Drs. Michael A'Hearn (University of Maryland) and Drake Deming (Goddard Space Flight Center), and this name is an amalgam of DIXI, comet observations, and EPOCh (Extrasolar Planet Observations and Characterization), which are observations of seven stars known to host at least one exo-solar system planet and the remote Earth. EPOCh data only are archived at MAST, while both EPOCh and DIXI datasets are archived at the PDS-SBN (Small Bodies Node at NASA's Planetary Data Systems), located at the University of Maryland. Some details of these observations are given on the MAST/EPOCh home page and supporting documentation from links or the menu gutter to the left of this page.

The data are organized to obtain observations of:

  1. exoplanet stars [HRII raw and irreversible calibrated flux images and light curves. These data may be downloaded from the PDS-SBN site or the MAST EPOCh data retrieval site. Please read the readme file for information on the times and the FITS file structure. Note that the light curve data are not yet a final product. They will be subject to a peer data review during the summer of 2010, and additions or changes to the header keywords may be made as a result of that process.

  2. Earth as a remote planet data [MRI and HRII images (raw, reversible- and irreversible flux) and HRII spectra. These data may be downloaded from the MAST EPOCh data retrieval site.

  3. calibration (raw) data. These data may be downloaded from the MAST EPOCh data retrieval site.

  4. documentation files.

Clicking on the "+" in the Data Retrieval site will take the user to a spider-tree" formatted directory layout; clicking on the ascii text descriptor will take one to a conventional directory table.

As noted in our configurations notes, the MRI is the Medium Resolution Imager (single filter centered at 7500 Angstroms), the HRII is the high resolution optical/near-IR imager that observed the Earth in intermediate band filters, and HRII is the optical-infrared spectrometer, observed through a "clear" filter. The spectral observations are two-dimensional in format (wavelength, spatial). The Earth was observed during three visits in early 2008 to provide HRII spectra and HRIV images and, for the March visit only, also MRI images. Two additional visits were made to the Earth in 2009. Negotiations are underway as to archiving the datasets resulting from these two visits at MAST, in addition to the PDS. In addition, a movie of the Moon transiting the Earth on May 28-29, 2008 may be delivered to MAST. Currently, movies generated by the EPOXI team may be found at their movie site. The stars hosting exoplanets were observed in a "clear" filter with the HRIV at a number of extended durations in 2008. Calibration observations were made starting in November, 2007 and during 2008, including after the Earth and exoplanet-star observations.

The data pipeline proceeded in three steps with the generation of a raw image, to a "radrev" (flux calibrated, reversible), and thence to a "rad" (flux calibrated and various instrumental artifacts removed). Except for the stellar (raw and radrev only) and calibration (raw only) observations, each observation is replicated in these steps.

Access to the data retrieval pages, MAST- and PDS-style formats, is through the Data Retrieval tab in the left gutter. A "spider-tree" directory structure enables expansion or contraction of the tree branches by clicking on the + or - symbol. Clicking on the text description enables browsing of the file (README), directory structure in conventional list format), or downloading (tar files). The exoplanet observations are segregated by MRI and HRIV imaging instruments or HRII spectrometer, state of pipeline processing, and by the three visits during 2008. For the Calibration directory there is a separate listing for the general target class (moon, stars, or unpointed, where unpointed refers to dark, sky, or stim-lamp) used to calibrate the star and Earth images. The star observations allow access to the light curves or the underlying image data used to extract them. The parallel data retrieval "PDS style" tab takes one to the data organized in exactly the same way as at the PDS site. Note that auxiliary readme files produced at MAST are not included here. However, the image data for the remaining stars, X0-2 and XO-3, are induded in the PDS-style site.

Any questions that MAST cannot or should not answer will be forwarded to the PDS for response.