Wfpc2 1 gyro test results
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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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Wfpc2 1 gyro test results

WFPC2 1-Gyro Test Results

Matt McMaster

Marco Sirianni


The test

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.


The analysis

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


Results

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


Results cont

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


Results cont1

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.


Results cont2

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


Conclusions

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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