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WFPC2 1-Gyro Test Results

WFPC2 1-Gyro Test Results. Matt McMaster Marco Sirianni. The Test. Program 11077 was initially designed for ACS/HRC using the TGM original program test as a template. 11077 was converted to WFPC2/PC by Matt McMaster maintaining an observational strategy very close to the original.

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WFPC2 1-Gyro Test Results

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  1. WFPC2 1-Gyro Test Results Matt McMaster Marco Sirianni

  2. The Test • Program 11077 was initially designed for ACS/HRC using the TGM original program test as a template. • 11077 was converted to WFPC2/PC by Matt McMaster maintaining an observational strategy very close to the original. • Attention was focused on the PC because the undersampling was less severe than for the WFs WFPC2/PC 0.46 mas (ACS/HRC 0.26 mas) • The program consisted of multiple exposures of two rich star clusters: NGC 5904 and NGC 6341. • Two sets of observation were taken, one on Jan 29 in 2-gyro mode and the other on Jan 31 in 1-gyro mode.

  3. The Analysis • The software developed for the TGM test was modified to be used with WFPC2 data. • The FWHM of the PSF for stars with S/N > 10 was calculated by fitting a gaussian profile to the stellar light profile • Resulted in tens to hundreds of measurement per image depending on exposure time and richness of the cluster • All of the measurements in each image were averaged to produce a mean PSF for the observation 2-Gyro 1-Gyro

  4. Results PSF FWHM distribution (unit: PC pixel -all data included) 2- Gyro Mean : 1.67 pix ± 0.16 Min : 1.13 Max : 1.99 1- Gyro Mean : 1.65 pix ± 0.14 Min : 1.09 Max : 1.89 The average PSF FWHM is remarkably similar indicating no obvious degradation inperformance in 1-Gyro mode

  5. Results – (cont.) As done for the TGM test, the dependence of the FWHM on exposure time, guide star brightness, and position on the sky was analyzed: There is no difference between images taken with a V=13 and V=14 guide star There are small differences in the PSF width due to the exposure time duration. Data from NGC 6341 only

  6. Results - (cont.) 2 – GYRO Exptime FWHM 10 sec 1.66 ± 0.03 100 sec 1.70 ± 0.03 400 sec 1.85 ± 0.04 1 – GYRO Exptime FWHM 10 sec 1.63 ± 0.02 100 sec 1.70 ± 0.04 400 sec 1.82 ± 0.05 Such differences were also noted during the original 2-Gyro on orbit verification test with the ACS/HRC.

  7. Results – (Cont.) The average PSF width in NGC 5904 data is systematically smaller than in NGC 6341, but there is no dependency on the gyro guiding configuration. A similar result was found for the clusters observed in the original 2-gyro on-orbit test with HRC

  8. Conclusions NGC 6341 /PC 1-Gyro mode F555W -100 sec There is no evidence that the quality of the science data obtained in 1-gyro mode is any worse than in 2-gyro mode.

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