The IKAROS observations are carrying out VLBI imaging in order to measure the proper motion of the IKAROS spacecraft. Together with the line of sight velocity from Doppler shifting,it will be possible to reconstruct the total velocity of the spacecraft and to test the performance of the solar sails.
To set up Hobart for these observations is fairly simple. The observations require RCP at two sky frequencies (8421 & 8431 MHz on 1/7/10 but check the VLBI Wiki on the day) using a new DAS profile (ho32_f.pro) and setting cDisko to record 2×32 MHz channels. These instructions are for remotely setting up the Mount Pleasant telescope (but apply equally if you’re there). Definitely check ahead of time (i.e before Brett and Eric leave for the day) that the Folly is connected correctly, that the frequency translator has SMY01 as LO1 and SMX_top as LO2 and that the BG3 cable is not connected.
- Get the schedule from the ATNF. You can do this easily with
./slogit.lba.pl on newsmerd. The experiment code will be on the LBA Wiki page (http://www.atnf.csiro.au/vlbi/wiki/index.php?n=Main.HomePage). If the code ends in an “a”, you’ll need to When the script asks you for a SEFD proc file, reply
systemp8425RCP.prc. Follow the instructions and it will drudg the schedule, put the files in the correct locations on hobart and print out a schedule summary and cover sheet.
- Select Rx6 from STOAT
- Check cryo levels, that it is set to “direct” and that the quadrature hybrid is out.
oscillator_control_gui.pl to set the Agilent to 14 GHz, 16 dBm
- Also set SMY01 and SMX_top to the appropriate frequencies for Sky1 and Sky2, with the levels set to 7 dBm. The Sky frequencies you need can be obtained from the LBA Wiki and the LOs can be calculated as LO = Sky - 7648 (in MHz).
calu -m sam26m to pass the cals to sam26m
- Go to
~observer/lovells_folly and run
./folly_interface. First, select
RF Switch 2 so that it displays an
O. If you’re in the control room you should hear a “clunk” as the relay triggers. Afterwards, the red LEDs on the RF switches should have the first, fourth, fifth and seventh lit up (previously is should have been the first, third, fifth and seventh). The default position (i.e X’s on the Folly Interface) is that the first switch is RCP and the second is LCP (The third and fourth are for selecting which SLD goes to the samplers, which we don’t normally use). Toggling them switches the polarisation that is passed through.
- Still using the Folly interface, adjust the attenuation to centre the DAS levels.
- If you are present at the telescope, check the programmable attenuators are correctly set to give a SLD reading of −4. If you are observing remotely, you will have to trust that no-one has fiddled with them too much (They are normally set to values (of ~12/2) that give the correct SLD levels for a well-centred DAS). If it’s badly wrong, then you will not get sensible Tsys measurements.
- if you have time before the experiment, it’s worth making some bruce scans on a strong calibrator. The CAL values that were loaded into the proc file assume 88 Jy in each channel (with a Tsys ~480–500 Jy). If your bruce scans indicate something radically different, change the value in the proc file, make a note on the log sheet and the wiki. Quit bruce before starting the main schedule.
- Assuming all has gone well, start up
cdisko.pl. Enter the experiment name, set the bandwidth per channel to 32 and select “Chans 1,2″.
- Start the Field System and load the schedule with
Once you’re onsource and recording via cDisko, let Chris (or Tasso) know when Hobart is underway so that they can run fringe-checks.
After the observation, make sure the dish is parked and it’s a good idea to reset the RF switch on the Folly.