Status of the NSO Aladdin Camera



nac pics nac drawings


NAC Operators Manual NAC Users Manual





Summary Prioritized Action List (updated 20050606)


1. Ship to Kitt Peak
2. McM/P Test: Evacuate
3. McM/P Cooling Tests
4. McM/P Imaging Test
5. Manuals from MKIR

Tests 01 Jun 2005


The agreement with the previous data is good. Read noise still about 3.3 ADU (53e-), gain still looks like 16 e-/ADU. Dark current may be up from previous tests to 200 e-/sec (13 ADU/sec). Optical bench temperature shows daily cycling of few degrees or less.





Summary Prioritized Action List (updated 20050309)


1. Fix dewar temperature drift. (Done)
2. Determine read noise and array gain. (gain = 16 e-/ADU, noise=51 e-)
3. Determine dark current. (50-60 e- per sec)
4. Fix the FITS header when sub-arrays are used. (Done)
5. Determine source of bright array corners. (MUX)
6. Write an up-to-date software manual.
7. Fix the error in the filename creation. (Done)
8. Reduce the 60Hz interference. (Done)
9. Large randomly occuring stripes (Not seen anymore.)

Light transfer image tests 31 Mar 2005


In general the agreement with the fits from the previous data is good. The extra noise in the first set of images was simply caused by the first image of the sequence having high ADU values.

IDL reduction script for LT data
The noise seems strange at 15,000ADU, but saturation seems to occur at 17,000ADU. The NOAO full well value suggests saturation at 23,800ADU.




In sequence data, only one set of 4 showed the horizontal and vertical striping. stest, s3test and s4test showed no stripes, s2test showed stripes in the first image again.

IDL reduction script for sequence


Light transfer and speed tests 25 Mar 2005


The light transfer data seems to show high noise levels at exposure times of 0.3 and 1.8 second exposures.

IDL reduction script for LT data
The speed tests are single read frames. The three different tests give speeds of 6.01Hz for 6Hz test, 7.92Hz for 8Hz test and 10.17Hz for 10Hz test.
The speed test show stripes in the 6 Hz and 10 Hz tests, but no stripes in the 8 Hz test.
10Hz, frame 0 - 400 10Hz, frame 1 - 400 10Hz, frame 2 - 400
6Hz, frame 0 - 400 8Hz, frame 0 - 400

The speed tests show a large decrease (600 ADU) in the counts from images 1 to 2, and then a slow drift of about 50 ADU over the remainded of the 500 image sequence.

IDL script for speed tests
An examination of the last 100 frames in the 8Hz speed test shows a strange pattern in the noise for each pixel. It shows the 8 pixel readout cycle clearly. The mean value for each pixel shows alternating bright and dark rows.
pixel stdev map, frames 300-399, 8Hz test pixel mean value map, frames 300-399, 8Hz test

IDL script for single read noise test


Light transfer and dark current tests 13 Mar 2005


Two sets of data were taken, files lt.00001-00062 and ltb.00063 - 00122 of a 256x256 quadrant. The first set were without light on the array, and the second had light. Each set contained five frames at each exposure value, from 0.1 sec to 300 sec. This was in DCS mode, and the array bias (VDETCOM - VDDVC) was 200mV.
For each exposure value the standard deviation at each pixel and the mean values were computed and plotted on the graph below. The horizontal line corresponds to a read noise of 3.25 ADU (52 electrons) and the sloping line corresponds to a slope of 1/2 (photon noise) and a gain of 16 photo-electrons per ADU. The data saturates above a full-well of about 50k electrons since the bias value was so low.

IDL reduction script for LT data
Dark current tests look like 2.5 ADU/sec or 40 electrons per second. The patterns on the image do look the same as when light illuminates the array; is there a light leak still?
IDL reduction script for dark data


NAC Status during MKIR visit 25-26 Jan 2005


In summary:

the Aladdin array was cold and in the dewar. We took many dark images with the array. The array characterization has not been done by MKIR and this is an important first step; the dark current, readout noise, linearity and operational bias voltage of the array must be determined before it can be used for science observations. The optical bench inside the dewar has a temperature drift which may reflect a small leak and this must be fixed. The array temperature control seems good (mK level). The filter wheel drive mechanism broke at the end of the first day and must be fixed. The filters seem reasonable, although the J-band filter seems to transmit more thermal background than desired, and strangely more background than the H-band filter. The software basic functions seemed to work, although the Redstar 3 control program crashed several times per day.

Array:


Noise:

The current estimate is that there are about 10 electrons per ADU. Estimates of the current random read noise are about 4 ADU. In addition to this there is a 60Hz noise at the level of 1-2 ADU. Action: read noise must be established with a light transfer curve, and the number of electrons per ADU must be firmly established with a light transfer curve.

Glow:

There are high counts at some bias voltages in two corners of the Aladdin array. This type of pattern is also seen in the NOAO dark current test data for the array. Action: examine if pattern changes with bias voltages with the filter wheel in the closed position to determine if the pattern is stray light or an array characteristic.


Dark current:

The dark current counts change with exposure time, but in almost all tests the dark current was on the order of 10 counts per second, contrasted with the NOAO test data which suggests less than 1 count per second. Action: run dark current tests at several bias voltage settings and several exposure values to determine if dark current is repeatable at an exposure and if there is an optimal bias setting for low dark counts.

Bias voltage:

The NAC array will need deep pixel full wells; this suggests the array should be run at a bias voltage of 800mV or greater. There is some concern that a particular type of bad pixel called a "ped" is on the array in the quadrant with several cross-like features. A ped can turn into a light emitting diode if the array bias voltage is turned up too high, and if this occurs the array must be returned to the manufacturer to have the pixel physical altered. Action: increase the bias voltage slowly, in steps of 50mV, from the current 500mV limit, taking test images at each bias setting; determine if the array can be operated at the 800-900mV bias setting without damaging the array.

Electronics:


60 Hz noise grounding problems:

A changing pattern of fringes apparently caused by 60Hz interference can be seen in the dark images from the array. The amplitude of the fringes is a few ADU. The fringe amplitude was reduced when grounding straps were applied to connect the ground level for the control computer and the analog electronics. During the last day when the filter wheel motor was removed, the amplitude decreased further, suggesting that the filter wheel drive motor ground level may also need to be tied-in. Action: tie-in the filter wheel drive motor ground to a common ground, and take further steps to reduce the amplitude of the interference.

Operating voltages:

See discussion above concerning bias voltages. Action: set the low, medium and high bias voltage default settings to safe but appropriate levels.

Readout clocking:

The dark vertical stripe separating two quadrants of the array appears to be an artifact of an improper array readout. Action: fix the array readout to correctly read these pixels.

Hardware:


Temperature drift: LN2 canister leak:

After initial cool-down, the temperature of the optical bench in the dewar reached 67K. However, after a few days the temperature slowly drifted upward to a level of 72K, and may drift to a higher temperature. The idea is that there is a vacuum leak in the LN2 pre-charge canister which allows some condensation to form on the radiation shield, which is thermally coupled to the optical table. Action: leak test the LN2 pre-charge can, retest under vacuum and cold conditions. If the drift is still present, replace the pre-charge can with a metal plate and fix the pre-charge can at a later date.

Broken filter wheel:

During the first day the filter wheel shaft became difficult to turn, and exceeded the torque capacity of the filter wheel motor. Action: determine where the shaft is binding and fix the problem.

Software:


Sub-array readout:

Sub-array readouts are currently limited to sections of the first quadrant. Action: NSO will check the documentation from MKIR in order to determine how to implement an arbitrary sub-array readout mode; NSO will implement this feature.

No manual:

A draft manual was not available; commands listed in the NICI draft manual did not operate in the NAC environment. Action: write a software manual with correct commands for the NAC environment.

Scripting command failure:

The scripting command system failed during several attempts: failures seemed to be associated with creating a unique filename for writing the data to disk. Action: find the error in the filename creation and testing and fix.

FITS headers lacking information:

During sub-array scripting procedures, only minimal FITS headers are written with the image data. These headers do not include vital information such as the image exposure time. Action: fix the FITS header production especially when sub-arrays are used.


Detailed Prioritized Action List:


1. Leak test the LN2 pre-charge can, retest in dewar with vacuum and cold conditions. If the temperature drift is still present, replace the pre-charge can with a metal plate and fix the pre-charge can at a later date.
2. Determine where the filter wheel shaft is binding and fix the problem.
3. Tie-in the filter wheel drive motor ground to a common ground, and take further steps to reduce the amplitude of the 60Hz interference.
4. Increase the bias voltage slowly, in steps of 50mV, from the current 500mV limit, taking test images at each bias setting; determine if the array can be operated at the 800-900mV bias setting without damaging the array.
5. Set the low, medium and high bias voltage default settings to safe but appropriate levels.
6. Find the error in the filename creation and fix it.
7. Fix the FITS header production especially when sub-arrays are used.
8. Establish the read noise with a light transfer curve, and establish the number of electrons per ADU with a light transfer curve.
9. Write a software manual with correct commands for the NAC environment.
10. Examine the bright corner pattern and see if it changes using different bias voltages with the filter wheel in the closed position to determine if the pattern is stray light or an array characteristic.
11. Run dark current tests at several bias voltage settings and several exposure values to determine if dark current is repeatable at a given exposure and if there is an optimal bias setting for low dark counts.
12. NSO will check the documentation from MKIR in order to determine how to implement an arbitrary sub-array readout mode; NSO will implement this feature.



Sample Data taken on 25-26 Jan



TEST 1


Sample light transfer curves/ dark current tests
Double correlated sample; cold filter stop #6
256x256 subarray starting at pixel 0,0 (?)

test.fit.18-???-q1.fit 0.3 sec, 5 images
test.fit.19-???-q1.fit 1.0 sec, 5 images
test.fit.20-???-q1.fit 3.0 sec, 5 images
test.fit.21-???-q1.fit 10.0 sec, 5 images
test.fit.22-???-q1.fit 30.0 sec, 5 images -- Strange banding
test.fit.23-???-q1.fit 100.0 sec, single image -- Stranger bands
test.fit.24-???-q1.fit 300.0 sec, single image -- Same as 22
test.fit.21 (mean) test.fit.22 (mean) test.fit.23 test.fit.24


TEST 2


Sample light transfer curves/ dark current tests
Single frames; cold filter stop #6
256x256 subarray starting at pixel 0,0 (?)


test2.fit.25-???-q1.fit 0.3 sec, 5 images
test2.fit.26-???-q1.fit 1.0 sec, 5 images
test2.fit.27-???-q1.fit 3.0 sec, 5 images
test2.fit.28-???-q1.fit 10.0 sec, 5 images
test2.fit.29-???-q1.fit 30.0 sec, 5 images
test2.fit.30-???-q1.fit 100.0 sec, single image
test2.fit.31-???-q1.fit 300.0 sec, single image, bottom rows strange?

test2.fit.25 (mean) test2.fit.31 (mean) test2.fit.26 expanded

IDL reduction script for test and test2 files



TEST 3


test of light_trans_short.rs3 script
(script failed, only writing two data files per exposure)
Single frames; cold filter stop #6

test3.8.fit and .fit.fe
test3.9.fit and .fit.fe
test3.10.fit and .fit.fe
test3.11.fit and .fit.fe
test3.12.fit and .fit.fe
test3.13.fit and .fit.fe
test3.14.fit and .fit.fe
test3.15.fit and .fit.fe
test3.16.fit and .fit.fe



IDL reduction script for test3 files




TEST 4


Linearity test, H-band filter, black window cover on
Bias voltage across the array: 0.499V
Deviates 5% from linearity at about 8000 ADU

atest.1.fit 10 sec
atest.2.fit 20 sec
atest.3.fit 30 sec
atest.4.fit 40 sec
atest.5.fit 50 sec
atest.6.fit 60 sec
atest.7.fit 70 sec
atest.8.fit 80 sec
atest.9.fit 90 sec
atest.10.fit 100 sec


atest.1.fit rotated Signal vs time Deviation from line

IDL reduction script for atest files



TEST 5


Disk speed writing timing test results:

8.52, 7.85, 7.88 full frames per second written during three consecutive minutes.
this exceeds the minimum 5 Hz rate specified in the acceptance document.

file listing
IDL reduction script


TEST 6


Single frames; 256x256 subarrays
no notes on this test; no integration times in FITS headers

noise.1-???-q1.fit 10 images
noise.2-???-q1.fit 10 images
noise.3-???-q1.fit 10 images
noise.4-???-q1.fit 10 images
noise.5-???-q1.fit 10 images
noise.6-???-q1.fit 10 images
noise.7-???-q1.fit 10 images
noise.8-???-q1.fit 10 images
noise.9-???-q1.fit 10 images
noise.10-???-q1.fit 10 images

noise.8-280-q1.fit Error vs signal

IDL reduction script for noise files





Five sample scripts written:
linearity.rs3
coadd_time_test.rs3
speed_test.rs3
light_transfer.rs3
light_trans_short.rs3


Data from 20050306


Coadd timing test, linearity test, light transfer test scripts run at MKIR. Data is analyzed.


Coadd Timing Test


A sequence of tests were run using coadd_time_test.rs3 . This varies the coadd number and the exposure time in order to identify the overheads associated with each. In each case a certain number of full sized (1024x1024) frames were summed into a buffer, then that buffer was written to a disk file with a time stamp.
For the one second exposures:
time [sec] = 0.871406 + 1.09880 * ncoadd
For the 0.5 second exposures:
time [sec] = 0.884925 + 0.598508 * ncoadd
The overhead of about 0.9 seconds must be for writing the file or other activities common to each loop and independent of coadd number.
Now fitting the slopes with exposure time gives:
slope [sec/frame] = 0.0982161 + 1.00058 * exposure
So for a zero second exposure the coadd rate is just 0.0982161 sec/frame which inverted gives 10.18 frames/sec.
This is above the minimum requirement of 10 frames/sec speed.

The streaks seem to line up on the array, even though the quadrants have different offset levels. An imaging test sure would be nice though.


IDL reduction script for coadd

Linearity Test


Subarrays of 256x256 size were used for this with the script linearity.rs3 .
The array looks linear to better than 5% up to raw counts of about 24000 ADU.

Unfortunately stripes develop in the images at counts of about 27000 ADU.
lin.00031-q1, 16410 counts lin.00060-q1, 27365 counts lin.00062-q1, 27619 counts


IDL reduction script for linearity test

Light Transfer Test



A set of 5 frames at a given exposure level were taken using sub-arrays sized 256x256 pixels to measure the noise at each pixel. The noise and the mean value at each pixel are plotted in the following figure.

Note that the noise has a large range at a given intensity; is this caused by background?
Also the noise decreases for the signals higher than about 22000 ADU. This is very strange behavior and currently unexplained.
IDL reduction script for light transfer


Acceptance Checklist (updated 20050309)


This section will provide a central checklist of all requirements for aiding the sign-off process.

3.1 FPA Mount Acceptance Test Checklist

  • FPA1: FPA socket and fanout board, housing, fiberglass supports and mounting bracket
  • FPA2: Cabling and connectors (lab test cabling)
  • FPA3: Cryo wiring and connectors
  • FPA4: Electrically shielded (Noise test)
  • FPA5: Baffled against stray light (Dark current test)
  • FPA6: Temperature sensor
  • FPA7: Heating (for active temperature control and warmup)
  • FPA8: Temperature controller (Dewar leak?)

3.2 FPA Control Acceptance Test Checklist

  • FPC1: Operate Raytheon Aladdin III 1024 ? 1024 FPA
  • FPC2: Fastest fame rate: 10 Hz (minimum, Single Read) about 15 Hz (target) (Single Read)
  • FPC3: Maximum exposure time: = 5 s
  • FPC4: All operations supported on either full array or single user-specified subarray
  • FPC5: Global reset mode
  • FPC6: Sampling modes
    • Single
    • Correlated double
    • Fowler (optional)
  • FPC7: Readout noise: using correlated double sampling, readout electronics to contribute = 25% to readout noise of FPA + readout electronics system at 1Hz frame rate (Light Transfer Test)
  • FPC8: User-programmable timing parameters
  • FPC9: Resistant to electrical interference (Light Transfer Test)
  • FPC10: FPA temperature selectable in range 30-50 K
  • FPC11: Readout of FPA temperature accurate to mK
  • FPC12: FPA temperature stable to about 0.1 K over 6 hours

3.3 Communication and User Interface Acceptance Test Checklist

  • CUI1: 1 TTL-compatible sense lines , electrically isolated (Demo?)
  • CUI2: 2 RS-232 full-duplex serial ports (for filter wheel control)
  • CUI3: 10/100 Ethernet connection for camera commands
  • CUI4: Stand-alone mode with graphical user interface and data display
  • CUI5: Remote Mode via Unix Socket (Demo?)
  • CUI6: Communication over networks via ASCII command sequences (Demo?)
  • CUI7: Image monitor with gain and offset correction Non-co-add mode: 6 Hz (minimum single read, no gain or offset correction) 12 Hz (target, single read) refresh rate (Demo with clock images?)

3.4 Data Acquisition and Storage Acceptance Test Checklist

  • DAS1: Support Flexible Image Transport System (FITS) data format including header parameters, comments, and image extensions (Time needed in header!)
  • CUI2: All modes to operate either with or without writing data to disk (Done?)
  • CUI3: Streaming mode - Record full or subsampled images on disk as fast as possible (5 image s-1 minimum single read, 10 image s-1 target, single read)
  • CUI4: Co-addition mode - Co-add 16-bit data into 8 (minimum) 16 (target) named, user selectable, 32-bit buffers (Done?)
  • CUI5: All modes executable via user written macros (Demo rabin mode)

3.5 Documentation Acceptance Test Checklist

  • DOC1: Computer-readable whenever possible
  • DOC2: System block diagram with system overview
  • DOC3: Mechanical drawings and specifications
  • DOC4: Electrical schematics and timing diagrams
  • DOC5: Software block diagrams and functional descriptions
  • DOC6: Annotated source code
  • DOC7: Users Manual
  • DOC8: Operators Manual
  • DOC9: Supporting manuals

3.6 Meetings/Reviews Acceptance Test Checklist

  • MTG1: Preliminary Design Review
  • MTG2: Final Design Review
  • MTG3: Final acceptance test plan
  • MTG4: Delivery, demonstration, instruction, and final acceptance at AURA facility

3.7 Other Acceptance Test Checklist

  • OTH1: One spare of each custom board(A/D spare board with only one A/D)
  • OTH2: Reusable shipping containers and packing lists
  • OTH3: 90 day Warranty