GALEX FUV PDF

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. A cross section of the instrument is shown in Figure 2 below. The adopted design meets the challenging requirements of providing moderate-resolution optics with a high throughput and large field of view in four different optical paths two UV simultaneous channels, with imagery and slitless spectroscopy modes , while keeping the instrument compact and simple to build and adjust. As needed for a SMEX program, special attention was paid to keep the concept tolerant to component positioning, especially for the moveable parts. 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. Allowance has been made for a small wedge on this aspheric window to compensate for the coma it induces in the NUV convergent beam.

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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. A cross section of the instrument is shown in Figure 2 below.

The adopted design meets the challenging requirements of providing moderate-resolution optics with a high throughput and large field of view in four different optical paths two UV simultaneous channels, with imagery and slitless spectroscopy modes , while keeping the instrument compact and simple to build and adjust. As needed for a SMEX program, special attention was paid to keep the concept tolerant to component positioning, especially for the moveable parts.

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. Allowance has been made for a small wedge on this aspheric window to compensate for the coma it induces in the NUV convergent beam. 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.

It turns out that the resulting deviation is low, a primary advantage to switch between imagery and slitless spectroscopy. This switching is performed by exchanging the grism with a low power plano-convex CaF2 imaging window.

These two components are mounted on a rotating wheel that also provides an opaque position, and is the only moveable part of the telescope. The grism and the imaging window positional tolerances are loose because they are dioptric components with only a low power. This low power is optimized to correct for the axial chromatism of all the transmissive elements.

The field curvature is cancelled by the power in the detector windows, and the detectors are tilted to the best plane. 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. There is no in-flight refocus capability.

The dichroic coating applied to the entrance face of the fused-silica aspheric corrector plate separates the FUV reflection and NUV transmission optical paths. This edge yields an additional factor of rejection of the NUV zodiacal light background above and beyond the natural CsTe detector photocathode cut-off.

The instrument integration, central processor, thermal control, test and project management were all provided by the Jet Propulsion Laboratory Pasadena, CA. A summary of instrument optical specifications is presented in Table 1. The two are basically identical, differing primarily in cathode choice and location as shown in the schematic diagram of Figure 5. The NUV detector has a Cs2Te cathode deposited over a thin metal layer on the inside of its fused silica window.

NUV resolution 5. Individual 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. The layers of the anode form a pair of orthogonal delay lines.

For faint UV observations, the combination of low background zero read noise and high red rejection that these detectors possess represents a favorable trade-off against the superior QE and field flatness of more conventional CCD detectors. Furthermore, MCP detectors do not require cooling, an important consideration in the contamination-sensitive UV band.

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GI observations will begin in late If there is any appearance of duplication, you will need to explain carefully feasibility section in your proposal why your proposed investigation does not duplicate the science objectives of the PI team. You may not need to obtain new observations; you may be able to use the data that will be released in Data Release 1 DR1 for an Archival Proposal. Mission 1. Even the small amount of residual atmosphere at the km GALEX orbital altitude scatters significant flux into the telescope. FUSE, the Far Ultraviolet Spectroscopic Explorer also has to contend with atmospherically-scattered sunlight and airglow, but its field of view covers about , times less sky, so much less of the scattered light enters the spectrograph.

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GALEX FUV PDF

Kilar During any visit or sub-visit observation the spacecraft attitude is controlled in a tight, spiraled dither. A gaelx of the GR7 subdeliveries are: 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. A summary of instrument optical specifications is presented in Table 1. Figure 3 above shows time-series telemetry plots for a set of observations described in Table 2. 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 fkv.

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