SHARC II Status/Schedule
Darren Dowell -- (626)395-6675 (office), -2600 (lab), 796-8806 (FAX)
Last modified Monday, 06-Mar-2000 06:37 PDT
cdd@submm.caltech.edu
SHARC 1.5 Goals -- 7 February 2000
SHARC 1.5 consists of a 1x32 bolometer array and as much of the SHARC II
hardware as is ready at the time of its installation at the CSO. The
goals will be to:
- Perform a 'test run' of SHARC II in Summer 2000, since the 2D array
may be a full year away.
- Fit check the hardware.
- Test new amplifier electronics and observing modes.
- Test the new acquisition computer and its interface with the antenna
computer.
- Demonstrate the promise of good sensitivity with SHARC II or identify
sources of lost sensitivity.
- Investigate the properties of atmospheric emissivity variations at
350 microns -- very important for total power readout.
The decision of whether to keep SHARC 1.5 at the CSO for observing
programs following engineering will be made at a later time.
The following summary shows goals/contingencies:
Detector
An unfolded pop-up bolometer chip is required, with at least 20 or so of the
32 pixels working. This item has not been officially promised from
Goddard. The bolometer array can be mounted on one of the ceramic
substrates we are acquiring to do tests of a prototype array in March.
Optics
The complete SHARC II optics is required, which involves filters,
a focal plane lense, an off-axis ellipsoid, folding plane mirrors, and
an enclosure, and a filter wheel. The filters and lense have been acquired.
An optical design exists but is in need of modification for the new
array format. The ellipsoid, enclosure, and filter wheel do not have a
mechanical design.
Millimeter Wavelength Pointing Pixels
We have two Spider Web bolometers to use for this, but we need feedhorns
and filters. To implement this will be a goal, but not a requirement, for
the engineering run.
JFETs
We need to have 32 JFETs, 1 for each pixel. Currently, no suitable modules
have been made, but we have parts on hand to do so: JFETs left over from the
SHARC II/HAWC sorting, ceramic packages left over from SHARC I, enclosures
and connectors left behind by Dominic Benford. (It is unlikely we would have
a SHARC II JFET module in time for Summer 2000.)
Amplifier
8 single-ended amplifier cards are needed to test total-power and
traditional chopping readouts. The single-ended PCB is currently on
order. Debugging and population of 8 cards remains to be done.
To test differential readouts effectively, we should go through a redesign
of the prototypes we have made to date. For a few pixels, we can use the
existing boards. This is a medium to low priority item, since a total
power readout is more versatile and desirable.
Other required components are already available: amplifier motherboard,
enclosure, bias board, thermometry board.
A/D
The partially-populated SHARC II A/D system is sufficient.
DSP/Acquisition Computer/Software
To get the acquisition computer, DSP hardware, and application software
working by Summer 2000 will be an amazing feat, but is possible. We should
try to get as much working as possible, but if we don't have enough to
observe, we can use the Mac-based DSP system as a backup with either the
SHARC or Hertz software. We should at least have the goal of testing the
interfaces to the antenna computer -- OBS commands, telescope position log,
etc.
Amplifier Programming
We have some leads on this, but no hardware suitable for an Nx32 array.
Dewar
The Dewar itself is in reasonably good shape for an engineering run. The
3He fridge support system is in place, and cycles under computer control
have been implemented under Windows/JAVA.
Shipping Container
We have a lead on a box for the Dewar, but haven't ordered it.
SHARC 1.5 Schedule -- 8 February 2000
Scheduling constraints:
- Walter Collins: after Sept. 24 (probably bad), after Aug. 13 (maybe bad)
due to school
- Planets: The summer is a good time for planets. For example, in
August 2000, Uranus transits at midnight, and
Jupiter and Saturn transit at sunrise. The Galactic plane from the Galactic
center to nearly Orion is also available. (Thanks to Darek for the plot.)
SHARC II Schedule
The delivery of the Nx32 SHARC II array from NASA/Goddard to Caltech is
currently scheduled for January 2001.
GUI description -- Deadline Feb. 29, 2000
Send description of GUI's we want in Goddard Instrument Remote Control to
Bob Loewenstein (HAWC) so that they can become part of software requirement.
(Walter, Matt, Attila)
Detector Tests -- March 22, 2000 to April 12, 2000
Goddard is to send us a bolometer array to test by the first date above.
Goal is to chose the thermal conductance and thermistor geometry that we want
and that HAWC wants. We are to send the results back by the second date.
See test plan for more details.
Necessary items:
- alumina boards -- on hand
- invar base, lid, and back cover -- on hand
- thermal suspension -- on hand; uses G10 tubes
- clip hardware -- on hand
- connectors -- ordered samples from SAMTEC Feb. 4, Feb. 24, Mar. 6
- copper heat strap -- will use OFHC on hand
- load resistors -- on hand. Enough for 2 modules?
- cryogenic cable -- unterminated 79-conductor cable in hand; needs
termination with two SAMTEC and two 25-pin connectors. Need two 25-pin to
SAMTEC jumper cables.
- RFI box -- on hand. Needs cabling.
- 2 JFET modules -- some parts on hand (boxes, lids, screws, springs, JFET
flatpacks). Need Kevlar guides (drawings to K. Lewis Feb. 25) and
mounting rack. Need assembly.
- amplifier cards -- PCB's on hand; need testing.
- bias board -- revised prototype undergoing testing.
- IV curve acquisition software -- not fully designed
- IV curve analysis software -- not written
SHARC II Component Status
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