Reset and OBST Commands for Chirp Transform Spectrometers 29 Nov 01 Initialize & Reset Instructions: If the PC that reads out the Chirp Transform Spectrometers is rebooted, one must log in to start the Chirp readout software: 1) Login as user smt (password mtgraham) 2) cd src/interface.smt/rPrePro 3) ./rPrePro3x CHIRP If the software must be restarted: 1) Type exit at the CHIRP> prompt. 2) ./rPrePro3x CHIRP OBST commands: There are three Chirp Transform Spectrometers (CTSA, CTSB, and CTSC). One can choose which of the three to use, which frontend's to connect to them, and which compression factor to use (1, 2, 4, or 8). (The compression factor applies to all CTS's. If it is > 1, the specified number of adjacent channels are added together before transmitting the data to BEORGA.) The BACKEND command interprets the name CHIRP to mean all CTS's. Or one can specify the CTS('s) desired with the names CTSA, CTSB, and/or CTSC. The BE_FE command specifies which frontend(s) to connect. When one single- channel receiver is used, the the RX command specifies to BE_FE that all three CTS's should be connected to that receiver. When a dual-channel receiver or two receivers are used, RX specifies that CTSA and CTSB are connected to the first receiver/channel and CTSC to the second receiver/channel. (The switches on the CTS down converter must currently be set manually to agree with this. The VAX can neither set nor sense these switches.) To override the defaults, use the BE_FE command: BE_FE CHIRP where is 1, 2, 1A, or 1B. The first of the 's is for CTSA, the second for CTSB, and the third for CTSC. Or one can change just one CTS's frontend with the command BE_FE CTS where is A, B, or C. To set the compression factor, the OBST command is CHIRP_WIDTH where is the number of adjacent channels to add together (1, 2, 4, or 8). The default width (specified in [SMT.ASTRO]CHIRP.SMT) is to add together channels in 4's. This is easily changed by changing the WID value in the file (#16). That value is the exponent of 2. So to get a width of 2, WID=1, of 1 is WID=0, and of 4 is WID=2. Changes in this file only have an effect when Kronen has been rebooted. It is thus recommended to use the CHIRP_WIDTH command in OBST as explained above. The data from the CTS's is sometimes trash. This happens most often with spectral line observing modes that wobble the subreflector like WSWITCH, especially if the wobble frequency, WFRQ, is greater than 1. But it also occurs in PSWITCH observations. The WSWITCH trash is most often characterized by negative numbers for the counts in many channels. The rarer trash found in both PSWITCH and WSWITCH modes has spectra where the mean level or RMS scatter is much different at the edges or the middle. Or every fourth channel will be different from the others. BEORGA normally applies a sanity check to the data. When it discards data, it prints a message on its screen and puts a message in the error log. An occasional discard simply reduces the subscan integration time by a few seconds. Of course, if all readouts are rejected the integration time will be zero and the scan will abort. The sanity check is controlled by the OBSINP command BAD8. The OBST command OBSINP BAD8 will set the sanity check parameter to the number . A zero turns it off entirely. A non-zero number means discard the readout if the number of negatives in the data exceeds abs(). A negative number also turns on the mean value and RMS sanity checks. The default for BAD8 is -10. Certain maintenance scans, like the center channel test, may require setting to a positive value or even 0. (Be sure to set it back to negative when done!) The sanity checker hasn't been throughly tested. If some trash is still getting through, please note the scan number and subscan number and notify Bill. If you think data is being discarded erroneously, also notify Bill. The following sanity check message may appear in the error log: CHPPRC DISCRD DATA 2 This means that readouts were discarded in subscan . Another problem with WSWITCH data is that the integration time in one throw may be different from the other throw. If it differs by more than 5%, the following warning message appears in the error log: CHPPRC IN TIM