The table below summarizes the usage of the antenna computer TTL signals in Bolocam mode:
| RX2 | Line | Function in Bolocam Mode | ||
|---|---|---|---|---|
| Pointed | Raster Scan | Drift Scan | ||
| 1 | Output 1 | |||
| 2 | Output 2 | |||
| 3 | Output 3 | Celestial / *Altazimuthal | ||
| 4 | Output 4 | |||
| 5 | Output 5 | Acquired | ||
| 6 | Output 6 | Tracking / *Idling | Tracking / *Scanning | Tracking / *Drifting |
| 7 | Output 7 | Rotate | ||
| 8 | Output 8 | New Observation | ||
| 9 | Input 1 | Rotator Busy | ||
| 10 | Input 2 | |||
| 11 | Input 3 | |||
| 12 | Input 4 | |||
| 13 | Input 5 | |||
| 14 | Input 6 | |||
| 15 | Input 7 | |||
| 16 | Input 8 | |||
| 17 | Signal Ground | |||
Two TTL signals, Output #7 and Input #1, are used to control Bolocam's dewar rotator from the antenna computer. The antenna computer rises Output #7 to trigger the dewar rotation. Bolocam keeps Input #1 at high level while the dewar is rotating. This handshaking takes place at the beginning of raster scans and drift scans when UIP is in Bolocam mode. Another TTL signal, Output #8, is set and reset by observers from UIP, and recorded by the Bolocam data acquisition computer, to indicate logical boundaries of data stream (e.g., new source, calibration).
In order to enable the handshaking for dewar rotation mentioned above, UIP has to be switched to the Bolocam mode:
UIP> INSTRUMENT BOLOCAM
Use the DRIFT_SCAN command to perform drift scans across the source. The example below causes the telescope to drift 600 " in right ascension, starting from 300 " west of the source and ending at 300 " east:
UIP> DRIFT_SCAN 600
To repeat scans, specify number of scans to the DRIFT_SCAN command, or use REPEAT_COMMAND command. For example, both:
UIP> DRIFT_SCAN 600 10
and
UIP> REPEAT 10 "DRIFT_SCAN 600"
result in 10 drift scans across the same source. Note that the dewar is rotated at the beginning of each scan.
To offset scans from the source, use either standard offset commands (e.g., RAO and DECO) or field offset commands (e.g., RAO /FIELD and DECO /FIELD):
UIP> DECO -10 UIP> DRIFT_SCAN 600 UIP> DECO 0 UIP> DRIFT_SCAN 600 UIP> DECO 10 UIP> DRIFT_SCAN 600
Use the RASTER_SCAN command to perform on-the-fly (OTF) scans across the source. The example below causes the telescope to scan at 20 "/sec in azimuth, starting from 300 " west of the source and ending at 300 " east:
UIP> RASTER_SCAN -300 0 20 0 30 /ALTAZIMUTHAL
Execute the following commands to initiate rotation of the dewar and wait for its completion:
UIP> FLSIGNAL 1 /BIT 6 UIP> FLWAIT 1 /BIT 8 UIP> FLSIGNAL 0 /BIT 6 UIP> FLWAIT 0 /BIT 8
The first command rises the line #7 of the antenna computer TTL output to initiate the dewar rotation. The second command waits for the line #1 of the antenna computer TTL input to rise, which indicates that the rotator is active. The third command lowers the line #7. The last command waits for the line #1 to fall, which indicates that the dewar rotation is complete.
Execute the following command at the beginning of each observation to rise the line #8 of the antenna computer TTL output:
UIP> FLSIGNAL 1 /BIT 7
Execute the following command at the end of each observation to lower the line #8 of the antenna computer TTL output:
UIP> FLSIGNAL 0 /BIT 7
The antenna computer records the telescope pointing information at 100 Hz and create log files. The disk where the files reside is exported using NFS. The Bolocam backend computer mounts the disk and reads log files directly, or an observer makes local copies if necessary.