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.
|Country:||Moldova, Republic of|
|Published (Last):||18 September 2008|
|PDF File Size:||17.20 Mb|
|ePub File Size:||20.47 Mb|
|Price:||Free* [*Free Regsitration Required]|
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. Background levels for non-DIS fields may be times higher, with a corresponding reduction in the exposure time to reach background limitation. With the lifting of bright star limits, a variety of areas previously gales were targeted, including completion of the AIS survey within the plane of the Milky Way.
Currently sub-visits are only used for all-sky imaging survey AIS and in-flight calibration observations. These included a number of redelivered GR6 data additional visits and associated coadds from onwardsalong with new tiles within GR7, which span approximately from Jan. Relative and absolute astrometric correction of satellite motion is performed in short s time intervals gslex stars measured by the NUV detector. Lim [m AB ] Gals est. The two are basically identical, differing primarily in cathode choice and location as shown in duv schematic diagram of Figure 5.
These products will use an improved pipeline, with updated calibrations, to handle changes in the response of the NUV detector in and A sample of the GR7 subdeliveries are: The last complete release was the GR6 late through mid for imaging supplements and the cuv survey.
This results in refined aspect solution which is used galfx determine where each time-tagged photon originated in the sky for both the NUV and FUV detectors. For some survey plans e.
For plans with sub-visit targets, a 20 second slew time is required to move between each leg of the observation. Ba seline survey sensitivities typically specified as 5 sigma for imaging and 10 sigma for spectroscopy are given in Table 1, above. These surveys are performed concurrently. Some observations are shortened by SAA passages when the detector high voltage must be kept at a safe, low cuv.
There was a problem providing the content you requested
A remarkable feature is that a unique blaze angle on the grism facets is found to provide a well centered efficiency for each channel, owing to the CaF2 index variation with wavelength. The dither spiral has the following angular rate profile: Aglex photons incident 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.
There is a catalog based on visits and another catalog based on coadds. Increased coverage of the Kepler field.
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. A summary of instrument optical specifications is presented in Table 1. For these observations the smooth variation in count rate vs.
In order to improve photometric performance, observations are dithered in a spiral pattern approximately 10′ in diameter at a rate of approximately 0.
A high-level description of data retrieval modes is provided on the Getting Started page. Furthermore, MCP detectors do not require cooling, an important consideration in the contamination-sensitive UV band.
Each orbit GALEX collects data during night segments eclipses of its orbits during visits to a single pre-programmed target.
Eclipses and are single pointing visits. The layers of the anode form a pair of orthogonal delay lines. 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. 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 gzlex scientific support was available.
The grism and the imaging window positional tolerances are loose because they are dioptric components with only a low power. After removing instrument overhead, each eclipse typically yields up to seconds of usable science data. This was fub 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.
Chapter 1 – Instrument Overview
Allowance has been made for a small wedge on this aspheric window galez compensate for the coma it induces in the NUV convergent beam. At these background levels, imaging surveys are background limited for exposures longer than 2 ksec [NUV] and 10 ksec [FUV] respectively.
GALEX performs its surveys with plans see Glossary for definitions of terms in bold that employ a simple operational scheme requiring only galxe observational modes and two instrument configurations. Dashed Spectra for galaxies with varying burst history young to old. From All Available Tiles. With the final data release GR7the AIS coverage of the sky was greatly increased, in particular at lower Galactic latitudes, thanks to a lifting of this safeguard towards the end of the mission.
Facebook Twitter Follow Us. Volume [Gpc 3 ]. 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.
Timing differences measured for the charge pulses at each corner of the anode are proportional to the position of the initiating photon event. This low power is optimized to correct for the axial chromatism of all the transmissive elements.