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Last updated
27 March 2002 08:35:45

Maintained by
martel


Printable version

Prism PR200L Dispersion on the HRC

AUTHORS : A.R. Martel, G. Hartig

PURPOSE :

The main goal is to measure the wavelength dispersion of the PR200L prism at several locations on the field-of-view of the HRC#1 flight detector.

LOCATION AND DATE : GSFC/SSDIF, Apr 9, 2001

INSTRUMENT CONFIGURATION :

ACS is in the TBF in the diamond configuration with RAMP+RAS/Cal at the entrance aperture, as in the acoustics alignment campaign. A diagram of the light source assembly feeding RAS/Cal is shown in Fig. 1. Light from a Hg line lamp is focused on the 4 micron pinhole by a MgF2 lens. Both the lamp and the lens are attached to the base of RAS/Cal to maintain the illlumination when moving to a different field point with RAMP. A 5461 Ang narrow-band filter can be inserted in the light path by one of the clean room operators (K. Redman or V. Roberts) to isolate the Hg 5461 Ang emission line. The move to the different field points with RAMP, and the associated metrology, is performed by the clean room operator.

METHOD :

The spectra were acquired at the H1, H2, H3, H7, H8, and H9 field points, which are defined in the acoustics alignment campaign. At each field point, dispersed spectra of the Hg lamp are taken, with and without the narrow-band 5461 Ang filter, as well as a direct image of the PSF through the F435W broad-band filter. The spectrum without the Hg filter was observed as a pair of images to increase the S/N ratio and remove the cosmic ray hits.

Examples of the spectra are shown in Figs 1-3. The spectra are oriented horizontally along the V2 axis, are ~100 pixels in length, and are offset by ~425 pixels towards the amps B-D edge from their nominal, undispersed field location. Hence, the target must be placed in the amp A-C half of the HRC field-of-view to insure that its spectrum is observed in the B-D half. The Fastie finger must also be avoided if not needed. The spectra run from right (amps B,D) (blue) to left (amps A, C) (red). The strong blue line is Hg 2537 Ang. The red end is very heavily blended because of the "bunch-up" of the dispersion, hence the need for the narrow-band filter to isolate the strong Hg 5461 Ang line.

RESULTS :

The HRC prism spectra were analyzed by the ECF group. Their results are presented in a series of reports.

CEI SPECIFICATIONS :

None.