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 benefit of scan mode was that it allowed the team to more rapidly complete galrx All Sky Survey in the ultraviolet. This results in refined aspect solution which is used to determine where each time-tagged photon originated in the sky for both the NUV and FUV detectors. At these background levels, imaging surveys are background limited for exposures longer than 2 ksec [NUV] and 10 ksec [FUV] respectively.
Because the satellite begins the eclipse inside the South Atlantic Anomaly the total exposure time is shorter than the maximum possible.
The instrument integration, central processor, thermal control, test and project management were all provided by the Jet Propulsion Laboratory Pasadena, CA. Background levels for non-DIS fields may be times higher, with a corresponding reduction in the exposure time to reach tuv limitation. Volume [Gpc 3 ]. All are in normalized units with the exception of UIT.
The dither spiral has the following angular rate profile:. As needed for a SMEX program, special attention was paid to keep the concept tolerant to component positioning, especially for the moveable parts.
This edge yields an additional factor of rejection of the NUV zodiacal light background above and beyond the natural CsTe detector photocathode cut-off. A high-level description of data retrieval modes is provided on the Getting Started page.
Relative and absolute astrometric correction of satellite motion is performed in short s time intervals using stars measured by the NUV detector.
For these observations the smooth variation in count rate vs. 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. In order to improve photometric performance, observations are dithered in a spiral pattern approximately 10′ in diameter at a rate of approximately 0.
Chapter 1 – Instrument Overview
The two are basically identical, differing primarily in cathode choice and location as shown in the schematic diagram of Figure 5. These two components are mounted on a rotating wheel that also provides an opaque position, and is the only moveable part of the telescope.
This motion is used for all targeted observations. During gxlex visit or sub-visit observation the spacecraft attitude is controlled in a tight, spiraled dither.
Observations for each survey type are scheduled based on target availability. After removing instrument overhead, each eclipse typically yields up to seconds of usable science data. As many as 12 sub-visits are allowed per eclipse period typical for AISwith all-sky survey sub-visits obtaining s exposure time per leg.
This was in contrast to the traditional boresight dither, known as the “petal pattern”, duv 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. The two instrument modes used for astronomical observations are imaging aka direct and grism.
[astro-ph/] Panoramic GALEX FUV and NUV imaging of M31 and M33
The final set of tiles, observed with the remaining NUV camera and predominantly observed after February 1, comprise the GR7. A somewhat smaller grism spectroscopic survey is also included.
There is a catalog based on visits and another catalog based on coadds. This switching is performed by exchanging the grism with a low power plano-convex CaF2 imaging window.
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For most purposes we recommend use of the galexView tool. A remarkable feature is that a unique blaze angle on the grism facets is found to provide a well centered efficiency for ffuv channel, owing to the CaF2 index variation with wavelength.
Increased coverage of the Kepler field. All-sky survey sub-visit eclipses and show discrete jumps in count rate throughout. For each sub-visit the spiral dither pattern is restarted. Lim [m Aglex ] Gals est.