1 Introduction

1.1 Purpose

This document describes the ING test requirements for the commissioning and acceptance of all new CCDS. As the generic test plan, some tests may not be relevant to a new detector on a particular telescope or focal station. This may be noted in any such test.

1.2 Scope

The tests can be divided into two broad categories:

1. Functional tests - designed to verify and validate the functional behaviour of the CCD within the Data Acquisition System.

2. Acceptance tests - tests designed to verify that the package is acceptable to the ING commissioning astronomer.

The functional and acceptance test will be carried out at the direction of the ING commissioning astronomer, although it is not expected that they will themselves carry out all the tests.

The test results will be fully documented, both in the condensed form of the CCD characteristics data sheet, and in the full form of the completed test plan to be held by the detector group.

Both the functional tests and the acceptance tests might be applicable to the testing of any subsequent modifications to the CCD and it's software - when only the relevant sections need to be carried out.
 

1.3 References

1. TEK4 Commissioning tests, RGMR.

2. TEK on INT/JKT - Testing, and Acceptance, PMF.

3. CCD Commissioning, DRM.

1.4 Overview

In the following sections the functional and acceptance tests are described in detail.

When carrying out the tests in the following, sections, the run numbers of any frames (and dates) evaluated should be recorded for future reference in the ING archive and printouts of relevant images stored with the commissioning file. One copy of this document will have "MASTER ccdname" on the front cover, and it is only in this copy that the results from each test should be recorded and the "tested" boxes ticked and initialled. This and all other documents created or completed during the testing and commissioning will be held in a ring binder labelled with the CCDs name - and "Commissioning" and held by the detector group for future reference. The detector characteristics sheets should be placed in the quality control folders in the control room of the appropriate telescope, along with copies of the Commissioning file. A WWW page will also be created giving details of CCD characteristics.
 
 

2 Functional Tests

2.1 Mechanical arrangement
 
 

MechU001 The cryostat should accept filler tubes of different lengths and be filled with liquid nitrogen and cooled.
 

Notes:

 

MechU002 LN2 filler tube location should allow LN2 to remain in the cryostat at all telescope positions. Put appropriate filler tube in and attach CCD to its nominal focus on the telescope. Ensure the cassegrain rotator is set to 0 degrees, and move the telescope to the positions shown and note any LN2 leakage and approximate hold times. This can be estimated by weighing the cryostat after the LN2 level has stabilised.
 

MechU003 The filler tube length needed for each of the various instruments that the device will be used on, should be recorded here, and a label fastened to the detector indicating these lengths.
 

MechU004 Capstans should have clamps on and with these clamps tight, the capstans should have no movement - both rotationally, and in slop.
Test completed OK Initial
 

Notes:

 

MechU005 Establish the position of the CCD surface relative to the window front face. and relative to the cryostat (metal) front face, and record them here.
Test completed OK Initials
 

Notes:

 

MechU006 The cryostat should physically fit all the instruments it could ever be used with. Note down here the instruments that have been tested.
 

MechU007 The flatness of the chip itself should be known. This should have been measured before delivery to ING. Check that there is no gross curvature across the chip by either FWHM measurements of stellar profiles ( if chip is to be used for imaging ) or through Hartmann shifts ( or FWHM estimates of arc lines if chip is to be primarily used for spectroscopy ) Note down the method used and the approximate shape of any curvature.
 

Notes:

 

MechU008 Flexure of the CCD relative to the sky should be noted for the most common focus for the detector. A full flexure test is not necessary for full commissioning, but the flexure between zenith and ~60 degrees from zenith should be noted and compared with what is expected. Advice from the appropriate instrument specialist can be sought.
 

Notes:

 

MechU009 It should not be possible for the radiation shield inside the cryostat to impinge on the light path, for any, of the likely foci that the detector may be used. Indicate here that this has been checked and is acceptable.
 

Notes:

 

2.2 CCD performance

PerfU001 The performance test should be carried out with a known set of CCD controller cards - record the serial numbers of all the cards and the rack.
 

PerfU002 The clock voltages and other telemetry voltages that are set-up for this detector should be recorded here. On the "Dutch" system, this is determined using, the "1 tele"' command. Also note down all the Bias voltages for this detector. Record the results below.
 
 

PerfU003 The DAS system should be able to start up and prepare for reading out the CCD. Start up the instrument control system, with the detector under test in use note down any errors or warnings.
 

Notes:

 

PerfU004 The bias readout time is needed for each readout speed. 'Using "BIAS" until the prompt returns, or until the system indicates that the run has completed. Leave blank any unsupported readout speeds. Note which DAS system was in use for this test.
 

PerfU005 The bias, level and readout noise in ADUs should be measured. with all lights off and curtain shut - preferably at night - take 2 bias frames at all available readout speeds. Using ING analysis scripts or any other means measure the bias level and readout noise in ADU. Note these down for all supported speeds. Keep the runs used.
 

PerfU006 Gain should be measured using the ING analysis scripts ( or the IRAF script ccd_gain ). This can most readily done using the preflash LEDs to provide the flat fields. Note down the gain and the electron readout noise at all supported readout speeds. Also note down the preflash time used. Write down the archived run numbers if applicable.
 

PerfU007 Bias structure needs to be checked. This is most clear on a MULTBIAS 10 or on 10 bias frames combined. This should be done at night to reduce the effect of light leakage. If it is not done at night ensure that any structure is not a light leak. It should be done for each speed at which it will be used in science mode (ie standard, quick and turbo) note down run numbers and dates.
 

Notes:

 

PerfU008 Any variation in bias structure should be noted. Take a bias frame whilst the telescope is tracking, derotating and autoguiding and with other sources of RF interference that are possible. Note down the conditions and the readout noise for this test, and any "banding" apparent on the frame. Note the run numbers.
 

Notes:

 

PerfU009 The linearity of the device should be known. Carry out linearity tests at all supported readout speeds. Note the integration times used, the resulting values. Draw a graph of the deviation from linear for all readout speeds and attach the graphs to this document.
 

Notes:

 

PerfU010-PerfU015 Binned readout mode. Carry out tests PerfU004-PerfU009 and note down the results when using the chip in 2x1, 1x2 and 2x2 mode.
 

PerfU016-PerfU021 Windowed readout mode. Carry out tests PerfUOO5-PerfU009 and note down the results when using the device is windowed. If the CCD is to be used on a spectrograph were a particular window will generally be used then this window setting should be used then this window setting will be used for tests.
 
 
 

PerfU022-27 If two-gain mode is available with this chip then the tests Perf005-009 should be carried out with the more ‘uncommon’ setting. Do 2 x 900 sec dark exposures at night. Note down the dark current and the run numbers used.
 

Notes:

 

PerfU028 Using the above frame estimate the cosmic ray count, in events per hour. The hot pixels intrinsic to the device can be found combining the images within IRAF with appropriate clipping parameters.
 

Notes:

 

PerfU029 Using the dark images taken in Perf028 produce a bad pixel map and attach a printout of the image with the look up table optimised to show the traps. List pixel co-ordinates of all traps and other poor cosmetics.
Test completed OK Initials
 

Notes:

 

PerfU030 Take a flat field exposure ( e.g. sky flat, lamp flat or dome flat ) and normalise the signal level to approximately unit. Attach a copy of this image to show cosmetics and the pixel to pixel response variations that cannot be seen in the dark images. Note the run number used.
 

Notes:

 

PerfU031 Calculate the pixel-to-pixel variations, using well exposed multi-flats in PerfU032. Show how the calculation was done.
 

Notes:

 

PerfU032 Calculate the charge transfer in all readout speeds. Using cosmic ray events, or transition region on flats. Include plots of cosmics and method of calculation.
 
 

PerfU033 The stability of the bias level and readout noise should be noted. The CCD-controller must itself have been powered up continuously for 24 hours, then without turning the drive box off, note down the bias level and readout noise (in ADUs) every 6 hours for 24 hours.

NB this should be done during the first S/D night when the chip or mosaic is on the telescope.
 

Notes:

2.3 Astronomical measurements and test

The astronomical tests to be carried out will depend on if the chip is to be commissioned at a

spectroscopic or imaging focal station. If spectroscopy then skip to section 2.3.2 and leave this

section 2.3.1 blank.
 

2.3.1 CCDs for use at imaging stations.
 

AstroImageU001 Find out where the optical field/rotator centre is on the CCD. Adjust to silicon centre if possible. Note down pixel co-ordinates, the instrument name and any telescope and capstan settings that effect this.
 

Notes:

 

AstroimageU002 Align CCD columns and rows with celestial co-ordinate system (e.g. by startrail tests) and note down capstan settings and any other parameters that may effect alignment.
 

Notes:

 

AstroimageU003 Establish optimum capstan setting for the detector at its most common imaging foci. If relevant, bear in mind the final position should allow TV and Autoguider to reach focus. Note down the capstan settings and telescope focus. (Lock the capstans after adjustment).
 

Notes:

 

AstroimageU004 Take standard star fields(s) in UBVRI filters and either reduce the data or inform the instrument specialist that the analysis needs completion. Note the run numbers. When the analysis is done make a note of the throughput here ( in standard units along with a brief explanation of the method )
 

Notes:

 

AstroimageU005 Establish colour correction terms. Note down the procedure used and the run numbers.
 

Notes:

 

AstroimageU006 Confirm the pixel size as projected on sky using a standard field. Calculate the pixel size as at the other common foci. Indicate which are calculated and which are measured
 

Notes:

 

AstroimageU007 Calculate the minimum usable exposure time on the focal station on which the device is to be used most commonly. This can be done by carrying out a linearity test at low shutter speeds. Write down the method and the results. As this is generally set by the shutter in the instrument itself it will not usually need to be recalculated for every CCD. The commissioning astronomer and the instrument specialist should satisfy themselves that this has been done for the station in question.
 

Notes:

 

AstroimageU008 Confirm that the de-tilting routines in the ING IRAF package are working satisfactorily with this device and that all tilt can be removed. Contact the instrument specialist to implement any changes necessary or with any other queries.
 

Notes:

 
 

2.3.2 CCDs for use at spectroscopic stations
 

AstrospectU001 Find were the centre of the slit corresponds to on the CCD if applicable ( this may not apply to all spectrometer usage) note row/column value. This can be done with a narrow dekker or a star.
 

Notes:

 

AstrospectU002 Ensure that the CCD can be focussed satisfactorily ie make sure that all tilt (spatial and spectral) can be removed an that hartmann shifts of <5um can be obtained across the focal plane. Ensure that the cryostat can be rotated so that arc lines can be aligned along columns (or rows) to within 5um ie that the top-bottom shifts over the full spectroscopic window are less than 0.2 pixels ( of a 24 micron pixel device. Note the final best focus run numbers ( a pair of hartmann images ) note the capstan settings.
 

Notes:

 

AstrospectU003 Confirm that the IRAF routines in the ING package work with this CCD and that the advice on direction and magnitude of capstan movements are correct. Confirm also that the collimator movement advice is correct and that the CCD can be focussed within the acceptable non-astigmatic region of the collimator. Contact the instrument specialist fro implementing these these routines and any other queries.
 

Notes:

 

AstrospectU004 Take exposures of a spectroscopic flux standard under the usual conditions for measuring throughput. this generally for measuring throughput. This generally means a wide slit, lowest spectral resolution possible plus no filters. Contact the instrument specialist in advance for the required set-up. Either reduce the data and note the results here or inform the instrument specialist of the run numbers and the setup used.
 

Notes:

 

AstrospectU005 Calculate the minimum usable exposure time on the focal station on which the device is to be used most commonly. This can be done by carrying out a linearity test at low shutter speeds. Write down the method and the results. As this is generally set by the shutter in the instrument itself it will not usually need to be recalculated for every CCD. The commissioning astronomer and the instrument specialist should satisfy themselves that this has been done for the station in question.
 

Notes:

 

AstrospectU006 Confirm the pixel size on sky by observing a pair of stars of known separation on the slit.
 

Notes:

 

AstrospectU007 Define the direction of movement along the slit viewed on the TV acq. system with respect to the CCD columns or rows e.g.. a movement to the right of the TV results in the object moving which way on the CCD.
 

Notes:

 

AstrospectU008 Confirm that the slit-to-detector reduction factor expected is reproduced with this CCD ie calculate what width of the slit should project to in terms of the FWHM of the arc lines and measure this at best focus position.
 

Notes:

 

2.3.3 Other device specific tests or comments.
 

Notes:

 

2.4 Software tests

SoftU001 The software should detect illegal windows and implement legal ones when requested. Try defining windows outside of the physical range of the device and note the software response and whether it is expected. Check that no windows are saved in the controller particularly window 0.
 

Notes:

 

SoftU002 The software should detect illegal attempts to bin and implement legal ones when requested. Try to bin in the following, way and note the software response and whether it is as expected: BIN 2x2, BIN 1000x1, BIN, 4x1 BIN 2000x2, BIN 1x4
 

Notes:

 

SoftU003 Check that all the information held in the FITS header is correct for this CCD. On the WHT the detectors definition file will have to have this detector added, along with the gains and readout noises for all readout speeds.
 

Notes:

 
 
 

3 Acceptance Tests

3.1 Delivery

The following items should be delivered:

        The cryostat with the CCD kinematically mounted inside and the preamplifier mounted in a box on its side.
 

Notes:

The following documents should be delivered with the new CCD

The manufacturers data sheet

3.2 Performance

The commissioning astronomer should accept that the chip is configured in an acceptable way

• The chip gain and readout noise is acceptable at the readout speeds available.

• The results from all the performance tests are acceptable (any deficiencies should be noted);

• The results from the astronomical tests are acceptable (any deficiencies should be noted);

• The results from the software tests are acceptable (any deficiencies should be noted, and improvements requested here),

3.3 Acceptance

If improvements have been agreed, or deliveries are yet to be received, this section should not be completed. If the CCD is acceptable in its current state, this document should be signed off by the people below.

Commissioning Astronomer (ING): (sign and date)

Commissioning, Engineer (ING): (sign and date)

Commissioning Engineer (Supplier): (sign and date)

Head of Engineering, (ING): (sign and date)
 
 
 
 

When this document has been completed. it must be held by the detector section.