Identical to Hertz data system but there need only be 18 data channels.
Cables to preamp should be shielded twisted pair teflon-insulated copper cable (Platt or Dragovan knows where to order this item). Length is 25 feet. (Giles will check this with call to CMU team. It may be more like 20 feet.)
(B) Viper computers:
(1) CMU control computer. The control computer the CMU uses is a Dec Alpha running UNIX, with display and some processing of data using matlab. Real time display under development. Communications protocol is tcp/ip with details of protocol to be made available on Viper web page.
(2) Comsoft PC. This controls the telescope and is under the command of the control computer.
(C) More on SPARO South Pole computer plan: Go to SPARO main menu and click on "Computers", and then "Plan for computer network" to see a fuller description of the data acquisition hardware, and also a description of our current plan for SPARO/Viper computer network
Must be able to provide a TTL signal output which will be used to drive the chopper on Viper via a Hewlett Packard arbitrary waveform generator. The demoduation is done with respect to this signal, with an arbitrary phase control. The frequency is controlled by the user.
The complete set of 3 computers must be able to acquire polarimetry data in the the standard Hildebrand-group polarimetry mode (one "nod" at each of N half-wave plate angles, i.e. 0 to 150 by steps of 30. A "nod" is a set of integrations taken at two predetermined sky positions, left and right, in the sequence L,R,R,L).
The demodulated data must ultimately be stored in the KAO data format so that we can use the rather specialized Hildebrand polarimetric analysis code (written in "c").
It must also be possible to run the system in the lab at Northwestern and acquire polarimetry data, again stored in standard KAO data format for ease of analysis.
The hwp controller will be available in the lab, and we also have a Sun UNIX workstation in the lab. Both are networked.
Aside from the rudimentary display modes already described, we may want to be able to show sine curves of "polarization signal" vs. hwp angle for each pixel. The polarization signal is computed from the demodulated data in a fairly straightforward way known to many polarimetrists, but I wonąt describe it here.
More on SPARO South Pole computer plan: Go to SPARO main menu and click on "Computers", and then "Plan for computer network" to see a description of our current plan for SPARO/Viper computer network