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About IMAPS Data


Currently, only the IMAPS-1 data is releaseable. IMAPS-2 was expected to become available but the data was never archived at MAST.


The original IMAPS data was stored as IDL unformatted data sets. The raw data was later converted to FITS format files by the staff members at the ADF (see NSSDC). The FITS headers were extensively modified by Goddard LASP personnel, and the resulting raw image files are now available via the WEB or anonymous FTP at in the /pub/orfeus/imaps/data/raw directory. An effort is currently underway by LASP personnel to archive the coadded, corrected raw data. These data are corrected for image distortion, face plate artifacts, etc. but the spectra must still be extracted (although wavelength assignments will be included). IDL software will be made available to read and extract data using these files.

IMAPS data sets are uniquely defined using the "Exposure Sequence Number". The first archived file is number 079 and the last image is number 721. The current naming convention is imaps1_0nnn.fits, where nnn is the exposure sequence number. The coadded files will use the naming convention imaps1_0nnn-0mmm.fits where nnn is the first coadded image and mmm is the last coadded image. (It is assumed that all intervening images are included in the coaddition.)

A table of the IMAPS1 observations (obtained from the EXPOLOG.DAT file written by Ed Jenkins) is shown below. The total integration time is an estimate for the total amount of observation time devoted to each object. The exposure sequence numbers describe the number and sequence of the individual observations. The numbers in parentheses indicate the number of frames used in the eta UMa exposures (511 frames were used for all others). Background exposures are not included in the table.

Time (sec)
Exposure Sequence
gamma2 Vel 1476 89-108
zeta Ori 2412 109-124
zeta Pup 1476 125-140
gamma Cas 1872 141-148
epsilon Ori 1836 150-173
alpha Eri 2088 175-194
beta Cru 946 356-375
eta UMa
(atmos. probe)
3432447-454 (511)
455-514 (255)
515-522 (511)
525-532 (511)
533-592 (255)
594-601 (511)
kappa Ori 3456602-649
beta Cen 288702-713

Spectral Resolution and Sensitivity

The plot below shows the spectral sensitivity and resolution of IMAPS compared to other recent UV detectors (courtesy of Derck Massa, Raytheon STX, Goddard Space Flight Center).