This site will provide support to GALEX guest investigator programs, FUV & NUV obtained simultaneously using dichroic beam splitter also acting as a field. NUV: Flux [erg sec-1 cm-2 Å-1] = x x CPS. To convert from GALEX counts per second (CPS) to magnitudes in the AB system (Oke ): FUV: mAB . GALEX uses microchannel plate detectors to obtain direct images in the near-UV (NUV) and far-UV (FUV) and a grism to disperse light for low resolution.
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The field curvature is cancelled by the power in the detector windows, and the detectors are tilted to the best plane.
During any visit or sub-visit observation the spacecraft attitude is controlled in a tight, spiraled dither. Background levels for non-DIS fields may be times higher, with a corresponding reduction in the exposure time to reach background limitation. This results in refined aspect solution which is used to determine where each time-tagged photon gales in the sky for both the NUV and FUV detectors.
The layers of the anode form a pair of orthogonal delay lines. A sample of the GR7 subdeliveries are: This motion is used for all targeted observations. But scan mode was performed at a time when the mission was operating on both minimal staff and budget, so while nominal data products were produced, the calibration pipeline was not optimized to handle these data, and no additional scientific support was available.
Eclipses and are single pointing visits.
SVO Filter Profile Service
Processing of observations made subsequent to February 1. The dither spiral has the following angular rate profile: GALEX performs its surveys with plans see Glossary for definitions of terms in bold that employ a simple operational scheme requiring only two observational modes and two instrument configurations. Dashed Spectra for galaxies with varying burst history young to old.
These two components are mounted on a rotating wheel that also provides an opaque position, and is the only moveable part of the telescope. GR6 Spectra are now available, click here to find out more.
The instrument is a 50 cm Ritchey-Chretien telescope with selectable imaging window or objective grism feeding a pair of detectors simultaneously with a multilayer dichroic beamsplitter.
Because the satellite begins the eclipse inside the South Atlantic Anomaly the total exposure time is shorter than the maximum possible. Some observations are shortened by SAA passages when the detector high voltage must be kept at a safe, low level.
Chapter 1 – Instrument Overview
Volume [Gpc 3 ]. Individual photons fuuv at the cathode set off an isolated avalanche of current inside parallel micron diameter microchannel plate MCP pores as they accelerate through a few-keV field. The last complete release was the GR6 late through mid for gaoex supplements and the grism survey. This Program is now chiefly of historical interest, except that the observations are currently being reprocessed and posted under the name of the “GII Survey” on these pages.
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Timing differences measured for the charge pulses at each corner of the anode are proportional to the position of the initiating photon event. All are in normalized units with the exception of UIT. Because GALEX records time-tagged photon positions with digitization that oversamples the instrumental PSF by a factor of 3—5the pipeline map accumulator can re-bin photon positions onto an idealized projection.
This was in contrast to the traditional boresight dither, known as the “petal pattern”, and to AIS modes in which the spacecraft hovered over single sky pointings and was reduced to a low voltage non-observing state when orienting between pointings. Users can familiarize themselves with GALEX data products by selecting, browsing, and downloading them from several search forms accessible from the Search and Retrieval tab on this page.
A cross section of the instrument is shown in Figure 2 below. Click here for a tutorial. At these background levels, imaging surveys are background limited for exposures longer than 2 ksec [NUV] and 10 ksec [FUV] respectively. Its wedge angle is adjusted to correct for the coma induced in a converging beam, simultaneously for orders 2 and 1 spectra of the FUV and NUV channels respectively.
GR6 Spectra are now available, click here to find out more Oct 07, This switching is performed by exchanging the grism with a low power plano-convex CaF2 imaging window. Each target consists either of a single pointing single visit observation or multiple adjacent pointings sub-visit observations.
Its reflecting entrance side corrects the FUV channel, whereas the exit side cancels the entrance side effects and brings in the required amount of correction for the NUV channel. For each sub-visit the spiral dither pattern is restarted. Ba seline survey sensitivities typically specified as 5 sigma for imaging and 10 sigma for spectroscopy are given in Table 1, above.
The top horizontal lines in red, green and orange, indicates eclipse, day and SAA periods respectively. The two instrument modes used for astronomical observations are imaging aka direct and grism.
A sample of the GR7 subdeliveries are:.