WIRO-GODDARD IR CAMERA MANUAL
UNDER CONSTRUCTION
Before the dewar has been pumped and cooled down, the rack-pc needs to be in the lab in order for it to track the temperature settings of the dewar. Afterwards, the rack-pc should be set up on the main platform in the dome because it must connect to the Cassegrain-mounted dewar. The camera can be operated from within the telescope control room via a connection to the rack-pc.
Once the rack-pc has been properly situated and booted in the dome, the following steps should be taken to connect from the control room.
IP addresses available for personal laptops are 129.72.212.{112 - 127}. Configure the TCP/IP information
as described above. To connect to the wireless router, the BAM key will be needed:
BAM keyword: 9294D80DF5CD66FB7906B638A2
If you need to ssh or telnet to a remote location (e.g. for email), the PuTTy program can be used.
Pumpdown/CoolDown Sequence
Pump down the warm dewar from atmospheric pressure using the turbo-molecular pump. Detailed instructions are given in the lab room. These steps should be performed by staff with cryogenic experience. Performing these steps incorrectly could result in costly broken equipment. Helium transfer requires at least two qualified people.
Note #1: In order to track the three temperatures (detector, cold plate, and filter wheel), one has to connect the cables from the electronics rack to the dewar and run the two vi's: Initports.vi and TempSensMonitor.vi.
Note #2: There are three temperature sensors. The relevant temperature is the detector's. When the
detector temperature approaches 90K, the pressure should be ~ 2 x 10-6. This is the time to
dump liquid nitrogen from both ports and refill as per the last step in Table 1 and
proceed as described.
| Pressure (torr) | ~ Time | Comments | 1000 | 0 min |
|---|---|---|
| 7.0 x 10-5 | 10 min | orange/green lights illuminate on pump |
| 3.0 x 10-5 | 20 min | fill both ports with liquid nitrogen |
| 2.0 x 10-5 | 1.0 hr | |
| 2.5 x 10-6 | 2.5 hrs | |
| 2.0 x 10-6 | 3.5 hrs | dump liquid nitrogen, fill outer with liquid nitrogen, inner with liquid Helium
Helium fill @ ~2.4 lbs; goose with Helium gas if necessary |
First, connect the two white and one of the black cables (labels: ) from the back of the rack-pc to the dewar electronics ports. Do not turn on the supply voltages at this time (switch is located on front bottom of the rack-pc).
If the rack-pc is connected to a remote computer (e.g. WIRO Prime Focus) via an ethernet cable, then it can be remotely viewed and operated from the control room using Timbuktu. Refer to the Computer Setup section which describes how to use Timbuktu.
More details will be added to this section.
Programs
LabView
Labview is the program used to run the VIs that operate the camera equipment. Run Labview on
the rack-pc (either remotely or locally). Labview is located on the desktop as National Instruments Labview 6.1
or you can find it under C:\Program Files\National Instruments\LabVIEW6.1\Labview.exe.
VIs
When you are prepared to aquire data, open the Acquisition_MulFowler_2.vi (C:\WIRO\Image). To take an image,
determine the integration time and enter it into the yellow box labeled "Integration (s)." Other variables
may be adjusted as needed. Then run the vi by clicking on the arrow in the top left-hand corner. An image
should appear when the red "Acquiring" button becomes a green "Complete" button.
The preamp box is connected to the detector via four small labeled cables. It is connected to the front bottom of the rack-pc via two larger black cables. To test the preamp, the large black preamp cables can now be hooked to the rack-pc. Turn the power back on. Run BAM Startup.vi (C:\WIRO\Startup), press TEST, and then run by clicking on the arrow in the top left-hand corner.
***If everything is OK, then plug in the three cables (lables: ) and run BAM Startup.vi again.
When it is time to run the telescope, you will no doubt need to know which filter you are using and how to change if necessary. It is important to note the following steps or else the voltage to the filter wheel will run constantly and heat it up -- reducing the lifetime of the cryogenics!
The detector works most efficiently at ~ 15K. The liquid helium, however, cools it to ~ 4K. A heater is connected to the detector in order to regulate its temperature which is monitored through TempSensMonitor.vi. The colder temperatures will not damage the detector; therefore, it is not necessary to heat until it is time to acquire data.
To access the heater, open Heater_Control.vi (C:\WIRO\Temperature). To deliver voltage to the heater,
increase the voltage under the detector knob at about 2V. This value is subject to refinement.
When the detector temperature reaches ~ 17K, turn off the heater by zeroing out the voltage and allow the
detector to cool to ~ 14K before turning on the heater again.
Initialize the ports by opening InitPorts.vi, located in C:\WIRO\Image, and run it. (There is a folder on the
desktop named WIRO, containing all the necessary vi shortcuts as well.)
Run the TempSensor Monitor.vi (C:\WIRO\Temperature) by clicking on the arrow in the
top left-hand corner of the gui toolbar and watch the temperature decline from ~ 77K to ~ 15K. When opening
the vi, if you do not need previous temperature data, check the refresh button before running. The time
increments are set at 1s by default but can be changed by renumbering the "Step (sec)" button. The
temperature of the liquid helium should reach down to about 4K; however, the temperatures of the detector,
filter box, and cold plate may read lower. This is because the temperature sensor is not precisely
calibrated. The lower plot can in most cases be ignored. It extrapolates the amount of time it will
take for a certain temperature to be reached. The operating temperature of the camera is ~ 15K.
