The CRSP Reference Manual
Return to CRSP User Manual
This manual is intended as a guide to those support personnel who are
involved with the installation, observing support, and troubleshooting
of CRSP. It is not an operating manual for the instrument, and
is complementary to the CRSP User's Manual
in that it covers aspects of CRSP which are not of concern to the user.
In addition, many of the procedures covered here,
particularly with respect to troubleshooting, are potentially
hazardous to the health of the instrument and should notbe attempted
by visiting observers or casual users of CRSP.
2. Instrument Storage -- The Big Box
CRSP, rotator, and all associated knicknacks are intended for storage
in a single large box. This box has wheels which permit it to be moved
about (with some difficulty), and two steel bars across the top by which
it may be lifted by crane hooks (one at each corner, outboard of the
large nuts) or fork lift. One may also transport the box
by fork lift from below, although care is required in inserting the forks.
Unlike IRIM, the internal structure of CRSP is not supported by the
cryogen fill necks, so there are no support tubes which must be inserted
before transporting, but care should still be exercised to avoid
excessive jarring of the instrument.
CRSP sits on a hydraulic cart, with the four instrument "legs" fitting
into guides on the cart table. Two of these have spring detents which
lock the legs into place. THESE MUST BE LOCKED WHEN THE INSTRUMENT
IS BEING ROLLED ABOUT, ESPECIALLY WITH THE ROTATOR INSTALLED. The
instrument/rotator combination is topheavy, and it could tip over,
with catastrophic consequences. The cart has a set of "elevated" wheels
which fit into U-channel guides in the instrument box; when the cart is all
the way in, it may be locked in place by two removable pins. In the initial
preparation steps, CRSP is detached from the rotator and moved around
separately on the cart; for installation on the telescope, CRSP and
rotator are moved together. Detailed steps will follow in the checklist.
Important -- Before the cart and CRSP are rolled
into the box, the cart must be in the FULL DOWN position, and the window
cover must be removed from CRSP.
Drawers and Cabinet
The box has a built-in cabinet, a large sliding drawer, and four small
sliding drawers for housing associated paraphernalia. Each of these is
marked as to the contents. The top two small drawers contain the
tools and alignment pins for installing CRSP. The third drawer
contains antistatic gear for use if the electronics must be
disconnected, as well as spectral calibration lamps.
The cabinet is used to store the ~ 12-foot cable wrapup connecting the
instrument to the Cassegrain J-box when the instrument is shipped
downtown. Two cables provide power to the
instrument, while the third is a bundle of six fiber optic cables.
THE FIBER OPTIC CABLES MUST BE TREATED WITH CARE. When installed,
they should be secured to prevent strain or tight radius (< 7 cm)
3. Installation Procedure
Although the mounting configurations of CRSP at the 2.1-m and 4-m
telescopes are quite different, the general installation and
removal procedures are similar. At the 2.1-m,
the CRSP/rotator installs directly to the nominal gold guider; at the
4-m, the back focal position of the f/15 secondary requires that
the CRSP/rotator mounts to the "white adapter" on its handling cart,
with an additional guider (which is effectively a spacer) in between.
The whole assembly is then installed on the 4-m guider using the
elevator. At the 2.1-m, the guider should be installed with the TV
mount to the South; CRSP should be installed with the fill tubes to
the North. On the 4-m, it is necessary to install CRSP with the fill
lines to the South for access from the cage door.
Fig. 1 Top View of CRSP
Fig. 2 Side View of CRSP
Fig. 3 Side View of CRSP, showing installation on Gold Guider
For continued happiness and long life, there are a few useful rules which
should be kept in mind when working with this instrument.
- Whenever CRSP and rotator are being moved about in the box, the CRSP
cart and rotator lock pins should all be properly in place. CRSP
should be jacked up against the rotator and the four bolts securing
CRSP to the rotator should be tightened up.
- Whenever the in-place cryogen fill tubes are installed on CRSP, exercise
care wheeling the CRSP cart in and out of the box, and in raising or
lowering the hydraulic lift, as it is possible to catch or bend them
on many obstacles.
- Once there is LHe in the CRSP, NEVER use N2 gas to
attempt to remove an ice plug in the cryogen line or to warm up the
cryostat after use (until one is positive the flask temperature is
above 77 K). Ice plugs in the LHe cryogen line may often be removed by
blowing He gas in the vent tube.
- Initial cooling of the LN2 and LHe flasks is best done
using a source of pressurized LN2, unless one has a lot of
time on his hands. Use moderation in filling, as excessive pressure
could damage the thin bellows in the cryogen necks.
Pumpout and Precooling
When possible, this should be started the day before a scheduled block
of observing time, since this permits adequate time for CRSP to
precool. Starting the day of a run will result in late installation
(at least 6 - 8 hours of precool are needed before filling with LHe),
and dark current will be elevated during the first night due to slow
cooling of some of the optics.
- Remove CRSP from box: make sure cart is supporting CRSP against the
rotator, loosen four 1/4-20 bolts securing CRSP to rotator (holes
are marked with blue). Slowly lower cart all the way, remove cart
lock pins, carefully roll CRSP out of box.
- Install window cover.
- Pump on vacuum jacket at least 1 - 2 hours, using Tribodyn pump.
- Close vacuum pump port and remove pump.
- Fill both CRSP flasks with LN2. The LN2 flask
will require some time to fill and will vigorously boil off for the
first couple of hours.
- After a couple of hours, top off LN2 in both flasks. The
cryogen should hold overnight.
- If the instrument is transported before final cooling, remove window cover
and install in box (see below). Transport, remove from box, and install
- Since the instrument is often tilted to extreme angles during telescope
balancing, do not top off the LN2 flask to more than half
capacity (~ 6 inches). This will prevent LN2 from spilling
out of the flask and possibly freezing the neck O-ring joint.
- Top off cryogen in LN2 flask to about half capacity.
- Using special tube, blow LN2 out of LHe flask, making sure
it is all gone. Wait a few minutes to allow any residual to boil off.
- Fill LHe flask with LHe, using standard U tube. The boiloff will be
quite high for about an hour, as the detector mount cools down.
It will require several hours and about 50% or so of the LHe fill to cool
the detector mount. During this time, CRSP may be reinstalled in the
box and moved to the telescope dome, if it is not there already.
- Top off LHe with standard U tube after boiloff has stabilized (optional).
- Install special cryogen fill tubes on CRSP. The LHe tube takes the long
insert; make sure the inserts are screwed in tightly. Use the teflon
gasket between the fill tube flange and the top of the dewar. Make
sure that the witness marks on the fill tube flanges line up with
those on the top of the dewar; this is necessary to clear the rotator.
- Align the fill tubes in the direction indicated in Fig. 1 (CRSP top view),
make sure window cover is removed and cart in down position. Roll cart
into box, being very careful not to bang fill tubes into anything.
- Carefully raise CRSP until it is against rotator, again watching out for
fill lines, which can be caught under rotator parts. Tighten down the four
1/4-20 bolts (blue holes) which secure CRSP to the rotator.
- Remove the three locking pins securing the rotator to the box and jack
up the cart so the rotator is raised about 2 inches.
- Remove the steel bar supporting the rotator in the front of the box and
carefully roll the cart out of the box. With the combined weight of
CRSP and the rotator, it is somewhat topheavy, so it is a good idea for a
second person to provide lateral support. Roll the cart under the telescope,
with the handle end to the South, and center the rotator
under the guider as closely as possible.
- Carefully lower the cart to its limit. Check that the rotator is properly
aligned for installation on the guider, using the white witness mark and
pointer on the bottom of the rotator on the SE side. Rotate by hand until
the two are lined up, if necessary.
- Install two guide pins at opposite sides of the guider.
They should not need to be threaded in more than a couple of turns.
- Remove plug in center of rotator.
- Make sure the telescope is at the zenith. Raise the observing platform
until the rotator is almost at the level of the guide pins
projecting down from the
guider. Adjust the cart until the guide pins will go into the corresponding
holes on the rotator. Raise instrument with the cart, guiding pins into
rotator holes, until rotator is snug against guider.
- Bolt rotator to guider with standard bolts (1.5 inch bolts are
long enough). Clearance is sufficiently
limited for some of the holes to require an Allen L wrench. After at least
three bolts are securely in, lowering the cart to take some load off the
instrument may make removal of the guide pins and installation of the
remaining bolts easier. Depending on the guider, 7 or 8 bolts can be
- Unlock pins securing CRSP legs to cart, lower cart, and reinstall it in
instrument box. Reinstall steel rotator support bar in box, clean up
other loose parts, etc.
- Check that rotator is properly bolted to telescope. Rotate instrument
manually to check that no bolts are improperly installed and interfering
with the rotator.
At the 2.1-m, the focal plane of CRSP is very close to the nominal
telescope focus (5 cm behind guider), and the normal focus range of
the guide probes is sufficient. The acquisition TV is used with a
custom lens with a f/15 pupil stop to reject scattered moonlight.
At the 4-m, the f/15 focus is about 30 cm behind the f/8 focus, far
beyond the range of travel of the guide probes or the acquisition
TV. A 2000 mm focal length lens must be installed on the guide
probe assembly to bring the f/15 beam to focus on the guide camera.
A similar lens mounted in a long tube is installed on the acquisition
TV to keep it within its nominal travel range. A secondary benefit is
some demagnification and a consequent increased acquisition field.
There are two sets of cables, a wrapup (3 cables) between the instrument and
junction box, and individual cables (4) from the DCU to
CRSP. They should all be in the instrument box.
- Make sure the instrument power supply is OFF before hooking up cables.
The instrument power may be controlled from the small switchbox in the
control room if the power switch on the power supply itself is in the
- Install telescope cable wrapup. The two power cables connect to the left
hand side of the DCU, as seen from the top (Fig. 1). The other ends go
to the Cassegrain junction box connectors "CCD Power" and "Aux Power".
Note: Do not connect the larger power cable to the "PS-10"
connector by mistake!
- Remove the teeny condoms from the fiber optic connectors on the
DCU, and hook the cables labeled "TRANS1", "TRANS2", "RCVR1" and "RCVR2"
to the similarly labeled connectors (the spares attach to the unmarked
connectors). After carefully routing the cables to minimize strain and
kinks, hook up the fiber cables in the same manner to the telescope fiber
connector panel. These panels are located on the S side of the
telescope at the 2.1-m and on the N side of the Cassegrain cage (4-m).
- Install Dewar Cables (refer to Figs. 2 & 3):
- Filter/Slit -- This is a Y-cable from the DCU to two 7-pin
Deutsch connectors on the Filter and Slit LEDEX motors.
- Grating Drive -- Another Y-cable from the DCU to the grating
drive motor and encoder. The plastic connector on the encoder cable is
- Rotator Drive -- Another Y-cable, the ribbon going to the position
encoder on the rotator, the 7-pin Deutsch to the rotator drive motor.
The latter cable should not be tied up too tightly, since the instrument
moves with respect to the rotator.
- Safety Limits -- A single cable from the DCU to a 10-pin
connector on the dewar case. Encodes the selected grating and safety
The electronics are sufficiently off center to require
additional counterweights on the
instrument to permit easy operation of the instrument rotator at large
zenith angles. Two sets of weights, one on the cover of the ACU, the other
above the LEDEX motors on the rotator, are sufficiently bulky that the
instrument cannot be installed in the cart with the weights attached.
The weights should be removed from CRSP when it is taken off the telescope
and stored in one of the drawers in the cart; conversely, they should be
installed after CRSP is put on the telescope.
The WILDFIRE electronics generate sufficient heat that they must be actively
cooled. The air vent fixture kept in the CRSP box should be installed on
the left side of the DCU (Fig. 1, 3). The vent hose (at telescope where
it exists) should be attached to this fixture and the vent fan turned on
before powering up the electronics. Alternatively, one may attach a fan
directly to the vent and exhaust the warm air into the dome at sites where
the vent hose has not been effectively installed.
Do your own thing, brah!
At the 2.1-m telescope,
this may be a good time to install the "Christmas Lights" on the secondary
and dress the cable so it can be accessed from the observing floor. These
are used in aligning the instrument to the optical axis of the telescope.
At the 4-m, the Christmas Lights" are permanently installed on the f/15
secondary on swing arms and are usually left in place. The lights
are accessed through the hatch on the side of the secondary cage.
At both telescopes, a custom controller box powers the lights.
4. Getting Started
Most of this is covered exhaustively in the
User's Manual, so only a brief
outline is given here, except for the Twist & Shout procedure.
The CRSP instrument power supply is located in the
computer room; with the switch on "remote", the power may be controlled by a
small switchbox next to the observer's console.
On the IR instrument computer (royal at the 2.1-m; khaki at the 4-m),
login as [telescope], with the current password. Execute
obsinit, choosing fire as the environment, and
enter the observer name and proposal ID.
- Logout and back into the computer. In the Instrument Control window,
enter startwf to bring up WILDFIRE; follow the interactive procedure.
The detector bias should default to 0.6.
- Check status of detector and instrument with status s
- If detector is below 77 K (det temp sensor reading > 0.99), activate by
pushing the blue button on the right side of the ACU (Fig. 1). The green
LED should be illuminated, visible through the hole in the ACU cover.
Twist & Shout
As long as the detector is sufficiently cold to activate, this operation
can be done in the afternoon. It need be done only before the first night
of a block scheduled run, and if the previous run was on the same telescope,
no actual adjustment may be necessary.
The purpose of T&S is to adjust the tilt of CRSP so its intrinsic
optical axis is aligned with that of the telescope. This is effectively
done when the detector can see all of the four "Christmas lights" at the
periphery of the secondary mirror, and that lights on opposite sides give
roughly the same signal. Because the lights may differ in intrinsic
intensity, and illuminate the detector differently along and across the
slit direction, it may not be possible to obtain equal signals for all
- On the 4-m, open the secondary and #3 mirror covers and check that
the guider mirror is in the "thru" position. The primary covers should
be closed. On the 2.1-m, check that the guider mirror is in the
"thru" position and open the primary covers just enough to permit
the instrument to see the secondary.
- Set up CRSP to the H band flatfield configuration (grating 1,
H filter, slit 1, 2300 ECU).
This should give significant signal in a short (1 s) exposure.
- At the 2.1-m, connect the light selector control to the PS-10
connector at the cassegrain J-box, power up the PS-10, and visually
verify that any or all of the lights can be selected. At the 4-m,
the controller box is powered by the AC line and the output goes
to a connector over the cage door.
- Turn all the lights on and take a 1 s exposure.
One should get a bright vertical stripe on the image
display. Cycle through the lights and check whether all lights
give some signal. You may want to reset zs for better visibility,
depending on the signal level.
- Check relative signals for opposite pairs of lights (1,3 and 2,4). If
the signal levels appear close for each pair and good signals are seen
for each light, the instrument should already be well aligned. At the
4-m, begin with the inner lights and work out to the outer lights,
checking symmetry at each layer.
- If one light of a pair gives much less signal than the other, the
instrument needs to be tilted in the direction of that light, using the
four bolts on the rotator (see detail, Fig. 4). You will need a
9/16" open-end wrench to do this.
- Loosen the (top) lock nuts on all four tilt bolts. The instrument is now
effectively supported by the bottom nuts on the bolts, and can be tilted
by adjusting them.
- Tilt the instrument toward the light giving less signal. Switch back and
forth between the opposite lights, checking the relative signals frequently,
until the signals are essentially the same. Fig. 5 illustrates a well-balanced
- Repeat the procedure for the orthogonal pair of lights.
- If adjustment in the second coordinate was necessary, go back to the first
pair and verify alignment, making small adjustments if needed.
- When alignment is complete, tighten down the lock nuts on the tilt bolts.
- Turn off lights, power down PS-10, disconnect light cable from connector.
At the 2.1-m, remove "Christmas light" assembly from secondary.
At the 4-m, it is necessary to move the telescope to the SE annex and
stow the secondary to flip the lights out of the beam if one is working
in the thermal infrared. CRSP should now be ready for observing.
Fig. 4 Detail of tilt adjustment bolts on CRSP rotator.
Fig. 5 Images of all four alignment lights in balance.
When all is well, the cryogen hold times for CRSP in powered up
configuration should be > 18 hr for the LN2 and > 14 hr
for the LHe. Filling at the beginning
and ending of the night should be adequate.
Keeping a cryogen fill log and measuring
the LHe level in
the storage dewar once/day is good practice, as it can prevent duplicate
fills and avoid unpleasant surprises.
5. Observing and Troubleshooting
The procedures for observing with CRSP are covered exhaustively in the
CRSP User's Manual.
For reference, proper values for status s
and typical readouts for ?filter and ped are
given at the end of this manual.
Troubleshooting is covered in Appendix III.
An exception is the procedure for recovering from a limit switch
activation, which is sufficiently critical to not be attempted by
the observer without consultation with the instrument scientist.
Grating Limit Recovery
Activation of any of the three grating limit switches; short wavelength,
long wavelength, or detent, immediately removes power to the grating
motor to avoid driving the grating into a hard stop and possibly shearing
the grating drive shaft. In the case of the long or short limits, the
grating must be manually driven, using the knob on the grating drive motor,
until it is backed out of the limit. It is imperative that the motor be
turned in the correct direction to recover from these limits.
Short Limit Recovery
Symptoms are a "short lambda limit" error message in ?filter
and a grating position readout < 100. To recover, turn the
knob on the grating motor CLOCKWISE and verify that ?filter
registers increasing grating positions. Continue until ?filter
no longer gives a "short lambda limit" message. Normal motor control
should then be possible.
Long Limit Recovery
Symptoms are a "long lambda limit" error message in ?filter.
The grating encoder may read a value > 4000.
To recover, turn the knob on the grating motor COUNTERCLOCKWISE and
verify that ?filter registers decreasing grating positions. Continue
until ?filter no longer gives a "long lambda limit" message.
Normal motor control should then be possible.
Detent Limit Recovery
In theory, this limit should never activate, although it is remotely
possible that one can change gratings without the detent engaging fully,
with subsequent motion vibrating the grating out of its detent. The
danger is that a partially rotated grating turret can impact the radiation
shield before the short wavelength limit is reached. This problem is
most likely to arise during a programmed motion; the symptom would be
a shutoff of the motor during the motion and an ?filter reading of
a grating position other than the programmed destination and a "detent"
error message. Recovery is in two steps:
- Manually move the grating motor to the change position of 4000 ECU. If
the error occurred during a motion, the actual position may be close to
that value. Use ?filter to check the position in this procedure.
- Push in the grating changer knob and attempt to engage the grating. If
the grating has rotated only a few degrees out of the detent, it may
be possible to engage it and seat it firmly in the proper position. The
"detent" LED should go out and ?filter should read properly.
- If that doesn't work, it is necessary to fish for the proper engagment.
On the grating change mechanism, back out the set screw next to the
changer knob; this set screw constrains the rotation of the knob unless
it is pushed in. When this is backed out, free rotation of the knob is
possible. Push it in at different angles of rotation until it goes in
all the way and the grating turret is engaged; it should now be possible
to rotate the grating turret back to the proper position. Since a 180
error is possible, make sure the indicator on the changer knob points to
the proper grating number as read by ?filter! Once
?filter reads that all is well, drive the set screw back
in, but not so far that it impedes rotation of the changer when it is
pushed all the way in.
6. Removal (Deinstallation) of CRSP
In general, removal of CRSP may be accomplished by reversing the installation
steps. Since time is usually an issue, many of the installation steps
do not have to be undone; for example, one may simply remove CRSP and the
rotator and install them in the box without removal of the cryogen fill
tubes. Below is a short list of important items:
- Before removing cables or the instrument, ensure that the detector has been
deactivated and the instrument power turned off. Usually the observer will
have been instructed to do so. If there is doubt, check the green LED in the
ACU; if it is on, it will be necessary to:
- Enter deactivate in the Instrument Control window
- Enter exit in the Instrument Control window (this should
return the hostcomputer prompt instead of "%")
- Turn off the instrument power supply
- Turn off the electronics vent fan and remove the vent hose (if installed).
Remove the vent from the DCU and store in the CRSP box
- Remove the counterweights from the ACU cover and the CRSP rotator and store
them in the CRSP box. CRSP will not fit in its box when they are installed
- Carefully disconnect the power/fiber optic cables from CRSP and the Cassegrain
junction box. Install the teeny condoms on the cable, DCU, and junction box
connectors. Wrap some bubble wrap around the ends of the fiber optic cable
to protect the connectors. Carefully roll up the cables and store in the
CRSP box or secure on the telescope
- The cables on CRSP may be left in place. However, we recommend removal of
the rotator cable, since a later removal of CRSP (without rotator) from
the box may damage this cable
- Make sure CRSP is rotated so the white witness mark on the rotator lines
up with indicator on rotator motor
- Remove the CRSP cart from the box and roll it under the telescope. Bring the
floor up until the cart is close to CRSP, then jack up the cart until the legs
are inserted in the guides in the cart and the cart is pushing against
CRSP with reasonable force. Engage the two locking pins
- Remove bolts securing CRSP rotator to guider, then carefully lower CRSP cart
all the way. Lower platform to clear telescope, then roll CRSP over to its
- Remove steel bar from CRSP box. Jack up CRSP cart until rotator clears top
of box, and carefully roll cart into box. Make sure cryogen tubes do not
- Install steel bar in box and slowly lower cart until three locking pins
securing rotator to box can be installed
- Install two locking pins securing cart in box
- Install plug in center of rotator
- Gather up tools, other items, etc., and store in appropriate drawers in the
CRSP box. Close and latch all the drawers. Install top covers
7. Useful Information
|CRSP InSb Status Display|
|Detector Temp = 1.099
||Detector Htr Power (mw) = 20.444|
|LN2 (cy7) = 0.938
||LHe (cy7) = 3.103|
|Stage (cy7) = 1.138
|VDet = -3.038
||VDDuc = -3.624|
|Voff = 0.444
|VDDout  : = -1.055
||VGG = -1.514|
|V3 = -2.686
|Data Offset 0 = -2.515
||Data Offset 1 = -2.002
|Typical ?filter Reply|
||grating is at position 2580|
||slit is at 380um (position 3)|
||rotator is at position 2179|
||filter is at j (position 4)|
|The limit switches are set to 0x008|
| Grating number 1 is in the beam|
|Typical ped Display|
|Alpha Nuti g1 K 2.280 microns 600s|
CRSP 2.1-m 29 Feb 1939
Temperature Sensor Calibrations
There are three types of temperature sensors in CRSP, all of which
operate on the principle of a temperature-dependent electrical
resistance. These sensors are biased with a constant current
(10 A) and the resultant voltage is read and
displayed in the Instrument Status window.
The LN2 sensor is a 1n914 diode which has a relatively
linear temperature/resistance relation from 50 - 300 K. The
sensor in CRSP apparently has a voltage offset, so the values in
the table should not be used to reference any other instrument.
The Detector sensor is a DT470 diode which has been
individually calibrated by Lakeshore over the temperature range
10 - 340 K.
The LHe sensor is a 5.1 K Allen-Bradley
resistor which has an exponential resistance/temperature behavior
at low temperatures. It serves as an "empty" warning indicator for
the LHe flask, since exhaustion of the LHe will cause the resistance
to drop precipitously.
CRSP Temperature Sensors
09 June 1999