DEIMOS
Quarterly Report
Number
18
October
1 to December 31, 1998
Fabrication of the new Element 8 continues with an expected completion date of March 1999. We then plan to have Element 8 coated in April 1999.
At the end of the quarter some work started again on the camera fabrication, we contracted the finish machining of the first barrel segment assembly. The assembly of lens elements into this barrel segment is expected to start in March 1999.
The design of the cells and carriage for the 6x8 gratings is complete. The design of the smaller assemblies and fixtures is in progress and we expect to complete all the major design work on the grating system by the end of Quarter 19.
No new work was done on the rotational drive or encoding system during this quarter.
The science CCD controller has been fabricated and tested in the Electronics Lab. Additional testing is continuing in the CCD Lab in preparation for installation of the controller boards.
talk tests with two Orbit CCDs in the test dewar was done during this quarter, and continues into Quarter 19. We expect to test the FC CCDs in the test dewar during Quarter 19.
No significant effort on DEIMOS software was possible during this quarter due to ESI. However, during Quarter 18 UCO/Lick software staff configured a database server for use on the Keck summit, which will be used by both ESI and DEIMOS.
The effort on ESI continued to heavily impact the DEIMOS schedule during this quarter. Once resources are again available to DEIMOS, the schedule will be reassessed.
The primary DEIMOS activity in the Optical Lab this quarter was the continuation of the polishing and figuring of the aspheric surface on the replacement lens of Element 8. The decentration tolerance of the asphere of .001" as reported by Curvmon as OFFCTR is remaining is good, as is the radius of curvature and astigmatism. At the end of the quarter, the "choppy" value (a figure of merit of how close the surface slope error is to the tolerance) was at 2.0, twice the tolerance. We expect to be finished with the figuring of the surface in March 1999, and then deliver the lens to Coherent for coating in April.
2.2 Mechanical Design
Filter Wheel
Filter wheel design is complete. The prototype holder was made and tested. The
fabrication drawings are nearly finished.
Gratings
Grating design is nearing completion although no fabrication was done this quarter
on the gratings.
Slit Mask
Slit mask modifications have been designed and drafting is in progress.
Dewar
No further design work is anticipated on the cryogenic circuit at this time.
Revisions to part # D7478 X motion arm (were the x motion drive shaft connects to the mosaic flexure assembly) of the dewar mechanical internal assembly have been designed to accommodate the interim board between the MIT/LL CCD flex circuit and the hermetic connector boards internal to the dewar.
A model of the CCD/flex circuit/interim board/hermetic connector assembly is being constructed to help realize assembly and packaging issues.
Design work was finished on the CCD housing and modifications are not anticipated at this time.
Dewar/Camera Mounting and
Assembly
After some flexure testing, it was determined that forces into the drive disk
must be minimized to reduce gross dewar/camera translation or rotation. This
resulted in the redesign of the "snout" support structure, (TV guider camera/snout
cladding structure) as well as the slit mask mounting base. The footings of
these items were moved from the inner drive disk to the outer ring of the drive
disk. This design work is complete, and a procedure for dismantling, modifying,
and reassembling the effected structures is being outlined. The camera assembly
tooling and fixtures for body-1 were also designed.
LN2 Cylinder filling assembly
Basic structural design is complete. Adaptations for ease of filling and safety
issues in the event a manual fill process must be implemented, as opposed to
the standard pressurized filling, are being considered. Also the issue of venting
while not allowing back flow of moist air during filling and "in use" boil off
is also under consideration. The use of a check valve or similar apparatus is
the current line of thought.
TV Guider
The support Structure has been redesigned as outlined in the Dewar/Camera mounting
assembly notes. The footings for this structure have been redesigned to reside
on the outer ring of the drive disk instead of the inside disk.
Coolant lines have been ordered and their implementation is as follows:
Implementing the "quick connect" fittings with this intermediate bulkhead establishes interchangeability with the ESI Photometrics PXL Camera as well as any other instrument using this camera.
2.3 Detectors
Lincoln CCDs
DEIMOS has a 3/8th share of lots 9 and 10 and we have begun testing lot 9 devices.
In most respects they are very good devices. However, we have found a serious
problem with charge transfer efficiency (CTE). At the normal operating temperature
(about -110(C) and normal clocking rates the charge transfer is poor (0.99995
or worse). CTE improves with higher temperature or with slower serial clocks,
and we have begun to explore the parameter space to determine if these devices
will actually be usable for DEIMOS. Gerry Luppino feels these CCDs may be usable
for direct imaging applications, but this has yet to be verified.
No lot 10 devices have been received yet, but Lincoln Labs feels they will show the same CTE problems. The poor CTE is believed to result from a contamination problem in the silicon, but the exact nature and origin of the contamination is unknown. Lincoln is actively investigating this problem.
Test results for the lot 9 devices can be found on anonymous ftp server gardiner.ucolick.org in /pub/ccid20/ where there are individual subdirectories for each CCD. These subdirectories begin with the three letters "ll9".
Lick/Orbit Interim Mosaic
CCDs
Two Orbit 2Kx4K CCDs have been successfully run in the test dewar. The crosstalk
tests on the Orbit CCDs have been completed. The crosstalk is dominated not
by the CCDs but by crosstalk within the two channels of a single video board.
Crosstalk between the CCDs was found to be acceptably low (~1 part in 10^5)
when only one video channel per video board is used.
Tests of the flexure compensation CCDs in the test dewar have not yet occurred, and is these tests are now expected to occur in February.
2.4 Software
Most software effort continues
to be directed towards ESI, but much of this effort also benefits DEIMOS. Work
on ESI's CCD control software, motion control software, user interface, test
suites, and documentation is complete with some integration testing yet to be
done. DEIMOS will employ practically all of this software as well.
Impacts
of ESI
As expected, ESI has consumed
nearly all software resources during this quarter. This was supposed to be the
last quarter devoted to ESI. However, because of ESI project setbacks that have
hampered the software/systems integration and testing effort, this trend is
now expected to continue through Quarter 19. Although ESI software is complete,
it has been difficult to identify substantive unfinished areas of the DEIMOS
software package that don't require significant support from engineering, which
is still fully engaged by ESI.
2.5 Electronics
A test fixture for characterizing and testing the Lick version of the SDSU-2 video boards was made. A linearity problem associated with high-amplitude signals was a result of an incorrect location of a diode on the Lick documentation. A performance enhancement was made to the dc-restore section of the circuitry to improve acquisition time and signal fidelity. These modifications are beginning to be installed on all the Lick video boards. Crosstalk between the two channels on a single video board was also observed. After careful analysis, it had been determined that this crosstalk is inherent in the board layout and cannot be removed. The amount of crosstalk is 1 DN per 20,000 DN of signal. We believe this crosstalk can be removed in software post-processing, but further testing will be required.
2.6 Flexure Compensation
No information available
2.7 Alignment
No progress was made this quarter on the Alignment.
No information available
[Tables and figures are not available via the web. Please contact Heather (heather@ucolick.org) for more information]
No information available
No information available
The following is a list of milestones for this quarter from the last Quarterly Report, together with the progress made on them:
Milestones for the next quarter: