Optical Monitoring Camera: OMC


Principal Investigator: Miguel Mas-Hesse, LAEFF-INTA, Madrid

with collaborating scientific institutes in Spain (INTA/LAEFF Madrid, U Valencia, U Barcelona), Ireland (UC Dublin), Belgium (U Liege), United Kingdom (MSSL Dorking), Czech Republic (Astroph. Institute)


The Optical Monitoring Camera OMC consists of a passively cooled CCD (2055 x 1056 pixels, imaging area: 1024 x 1024 pixels) working in frame transfer mode. The CCD is located in the focal plane of a 50 mm (diameter) lens including a Johnson V-filter to cover the 500 - 600 nm (CCD: 850 nm) wavelength range. The OMC is mounted close to the top of the payload module structure. The OMC observes the optical emission from the prime targets of the INTEGRAL main gamma-ray instruments with the support of the X-Ray Monitor JEM-X. The OMC offers the first opportunity to make long observations in the optical band simultaneously with those at X-rays and gamma-rays. This capability provides invaluable diagnostic information on the nature and the physics of the sources over a broad wavelength range.

For more details we refer the interested reader to ISOC's Announcement of Opportunity documentation of the OMC Observer's Manual and to a sequence of papers on the OMC payload in the A&A Special Letters issue on: First science with INTEGRAL. This issue also contains various other papers on the first results from in-flight observations. A detailed description of the instrument can also be found in the OMC Analysis Scientific Validation Report, part of the OSA documentation (http://isdc.unige.ch/index.cgi?Soft+download).


Optical Monitoring Camera OMC page at LAEFF/INTA Madrid, Spain
OMC Science Archive at LAEFF/INTA Madrid, Spain



Overview of scientific capabilities of OMC

Wavelength range 500 - 600 nm (Johnson V-filter)
Field of view 4.979° x 4.979°
Aperture 5 cm diameter
Focal length 153.7 mm (f/3.1)
Optical throughput > 70% at 550 nm

Stray light reduc. factor* (within UFOV^)

<< 1e-4 (no stray light detected)
Detector 50 mm lens + CCD (2055 x 1056 pixels),
imaging area = 1024 x 1024 pixels
Pixel size (13 x 13) μm2 = (17.5 x 17.5) arcsec2
CCD Quantum efficiency 88% at 550 nm
CCD full well capacity ~120000 electrons/pixel
Angular resolution ~23" Gauss PSF (FWHM=1.3±0.1 pix)
ADC levels 12 bit signal, 4096 levels:
~30 cts/digital level (low gain)
~5 cts/digital level (high gain)
Frame transfer time ≈2ms
Typical integration times 10s - 50s - 200s
Time resolution >3s
Limit magnitude 18.1 [V, 10x200s, 3σ]
18.9 [V, 50x200s, 3σ]
19.3 [V, 100x200s, 3σ]
Photometric accuracy 300 s
Point source location accuracy ~2"

* This parameter defines the factor by which the flux from any source within the UFOV (but outside the FOV) is reduced by multiple reflections before reaching the detector surface as background light.
^ The unobstructed field of view (UFOV) defines the angle which has to be clear to space in order to avoid reflected light directly reaching the optics.


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