EngPlan_11Jun2003

Detailed plans for K2 enginerring 2003, June 11

PXL replacement for SSC testing per T. Nordin

1. Scope

This document details the tasks used to determine the performance of the K2 f/40 Photometrics PXL guide camera as compared to the Star Stacking camera (SSC), a Photometrics series 200 camera. There are five parameters to examine in determining if the PXL camera is a suitable replacement. These parameters are 1) Camera pointing origin alignment, 2) Noise, 3) Photometric response & sensitivity tests, 4) Plate scale tests, and 5) Primary mirror focus mode tests. This document covers data collection only, data reduction and analysis will be covered in a future document.

2. Overview
a. SSC
The K2 SSC is a Photometrics Series 200 system with a CH-250 camera head. The 12-bit camera uses a Thomson CSF TH-7863A, 384 column x 576 row frame-transfer CCD. The light sensitive area is 384 x 288 (H x V) pixels. The CE200 to CC200 cable length is 300 feet, which requires that the 200kHz nominal scan rate be reduced to 180 kHz, yielding a readout rate of 0.6 seconds per frame.
From the Factory Test Report:
Dark Current is 52e-/sec @-30C.
Gain is 54.24 e-/ADU.
Read noise is 29.22 e-
Well capacity is 222k e-
Pixel Size is 23 um
Quantum Efficiency at 650 nm is ~27%

b. PXL
The K2 f/40 guide camera is a Photometrics PXl system with a SITe SI-003AB uncoated, 1k x 1k, back illuminated CCD, with 16-bit digitization. The scan rate is nominally 200 kHz, yielding a 5 second readout rate.
From the Factory Test Report:
Dark Current is 2e-/pixel/sec @-40C.
Gain is 5.1 e-/ADU at 1x (selectable to 1x, 4x, 8x, 16x)
Read noise is 14.3 e-RMS at gain = 1x
Well capacity is 300k e- MPP
Pixel Size is 24 um
Quantum Efficiency at 650 nm is ~80%

c. Current uses for the SSC
The SSC is the primary camera used to verify telescope pointing. This camera is mounted before the elevation journal, which effectively eliminates the effects of the elevation journal flexing while pointing. Additionally, the SSC has no rotator, eliminating the effects of that axis. Essentially, SSC is as optically close to the primary is as practical. The SSC is also used to verify image quality after segment exchanges.

d. Performance requirements for the SSC
i. Unknown, testing to find current specifications.

3. Off-Sky Tests
Several of the basic performance tests can be performed off-sky. These tests are to be performed using XGUIDE, on both cameras. These tests will be used to evaluate dark current and noise.
a. Dark field, to determine dark current performance.
i. Verify the camera is in a dark environment, and record frames at the following settings:
1. Binning: 1x1, Integration Time 1-msec
2. Binning: 1x1, Integration Time 120 sec
3. Binning: 1x1, Integration Time 1-msec
4. Binning: 1x1, Integration Time 120 sec
b. Flat Field, to correct for pixel performance. These tests are to be performed on both cameras.
i. Set the camera into a flat imaging field, verify at least 1000 counts with no pixels saturated, and record frames at the following settings:
1. Binning: 1x1, Integration Time (set for desired counts)
2. Binning: 1x1, Integration Time (same as 3.b.i.1 above)

4. On-Sky Tests
The following tests must be performed on-sky, with both cameras.
a. Camera Collimations:
i. Set-up on a star and collimate the camera.

b. Sensitivity and Photometric Response Comparison
We wish to determine the basic parameters of the SSC/PXL in terms of sensitivity and noise. The various tests should all be done storing the full FITS frames for off line analysis.

i. Photometric response (both cameras)
1. With a 5th mag star, and with the image in reasonable focus, take and store image with integration times of 10ms, 30ms, 50ms, 100ms, 300ms, 1000ms, 3000ms, 10000ms. Use the shutter for this set of measurements.
2. With a 9th mag star repeat i) above.
3. Using stars in the 7-9mag range with known spectral types, take and store images of 5 different stars, checking that the detector does not saturate. Pick suitable integration times for this.
4. Repeat on the same stars for the PXL.

ii. Sensitivity tests (PXL guider only)
1. Locate a 14th magnitude guide star from the GSC, about 2 hours east of meridian. Note its magnitude.
2. Take a 2x2 binned, full-frame image. Note the total or peak counts and the integration time.
3. Guide on the star for 3 minutes.
4. Find another star about 1 magnitude fainter (i.e. 0.4 x the counts/sec).
5. Repeat steps 2-3. Note that you will not be able to use GSC stars after the first one or two; you will need to find random field stars that give approximately 0.4 x the counts of the previous target.
6. Continue with fainter stars (each about a magnitude fainter) until you reach a point where you can no longer find fainter stars.

c. Plate Scale Comparison test (both cameras)
We wish to determine the guider plate scale (which is nominally 0.048 arcsec/pixel). This will be done using several astrometric binaries provided.
i. Set up on one of the 20-40 arcsec binaries in /kroot/starlists/000_astrometry, and center the image.
ii. Adjust exposure times to give reasonable S/N without saturating, save a 2x2 binned FITS files for off-line analysis.
iii. In turn, move the image to each of the four corners of the display, and save a 2x2 binned image. You should have recorded five total images.
iv. Repeat for other binaries

d. Non-Vignette Verification (both cameras)
i. Put a 6th mag star on the camera
ii. Piston the secondary by -3mm to make a nice image of the primary in the detector, approximately filling it. Adjust the integration time as needed.
iii. Save a FITS for each camera.

5. Schedule
a. On sky tests are scheduled for 18 April, 2003 for both cameras.
b. Off sky tests are scheduled for the morning of 19 April 2003.
6. Follow-on Actions
a. If testing proves successful, pointing and image quality tests will be migrated to the f/40 guider.
b. If testing proves successful, the K2 SSC will be removed from the telescope, and reserved as a back-up system for the K1 SSC.

Reference Documents

1. Interfacing Visitor Instruments at the Keck II F/40 Bent Cassegrain Port Manual
2. Keck 2 Guide camera Selection Requirements. R. Matsuda, 7/12/96
3. Photometrics Series 200 user’s manual, 1/1989
4. Photometrics PXL System manual. 57-010-002 Rev D
5. Keck On-Sky Engineering Tests:
a. T213, Star stacking camera sensitivity
b. T667, Quick verification of rotator zero and REF pointing origin
c. T794, f/40 focus functional tests
d. T796, f/40 scale measurements using SSC
e. T812, K2 f/40 (RBC2) rotator zero point and limits
f. T814, K2 f/20 RBC2 guiding accuracy and sensitivity.
g. T815, K2 f/40 guider pointgin origin and collimations
h. T818, K2 f/40 determine guider scale and verify rotator zero
i. T820, K2 f/40 guider daytime checkout
j. T848, SSC Plate Scale Test

Detailed K2-AO performance optimization plans per Marcos van Dam

Objectives:
- Verify that the DM and TT loops are decoupled.
- Investigate if changing the controller improves things.
- Obtain the best possible Strehl on a bright star.
- Find the magnitude of the noise and bandwidth error terms.
- Compare the 1.0” plate scale.

Choose a bright star (V=6) near zenith.
Reconstructor: Bayesian,
Optimize the gain parameters.
Push the TT Gain high and verify that it does not interfere with the DM loop.
Change the leak parameter.
Change the controller parameter.
Change the CCD focus.

Reduce the frame rate, keeping the gain constant at (0.4,0.6).
400 Hz
200 Hz
100 Hz (if possible)
55 Hz (if possible)

Repeat the frame rate experiment with a V=10 star.
Optimize the gains.
Change to 1.0” plate scale.

Repeat the frame rate experiment with a V=11 star.
Optimize the gains.
Change to 1.0” plate scale.

Repeat the frame rate experiment with a V=9 star.
Optimize the gains.
Change to 1.0” plate scale.

Repeat the frame rate experiment with a V=8 star.
Optimize the gains.