VSOP Data Reduction | HALCA calibration | GRT calibration

Ground Radio Telescope Calibration

System Temperature Measurements
Gain Curves
Phase Calibration Tones
Nominal Tsys and Gain Information

HALCA calibration is described on a separate page.

Last modified: 4 April 2000

System Temperature Measurements

The system temperature of ground radio telescopes is monitored during each observation. Some telescopes continuously inject a known low-level Noise Adding Radiometer to determine the system temperature: other telescopes switch a strong noise diode in and out of the signal path less regularly. These system temperature measurements should be recorded in the GRT logs files. These log files are placed on the GRT's regional server soon after the observation. Details of the regional servers for GRTs participating in VSOP observations are given in the tables below.

Some GRTs will covert the system temperature information into the `ANTAB' format which can be read directly into AIPS. ANTAB files for EVN telescopes are prepared after each EVN block session. Accessing calibration data for the VLBA and VLA is described in this memo (link disconnected). For other telescopes it is often necessary to run the log2ant script developed by Frederik Rantakyro. This script (and accompanying documentation) is available from the ANCAL directory of the EVN regional server.

The regional servers for GRT logs are shown in the Table below. IP addresses for these FTP sites are given in Table at the bottom of the page. The sub-directory containing the logs on most servers is of the form mmmyy, where mmmyy is the month and year of the start date (UTC) of the observation, e.g. sep97. A number of the regional servers are password protected.

Note that the * signifies that nominal Tsys and/or gain information for this telescope is available further down this page. (Some of information is obsolate at 2019.)

**GRTs and their Regional Server for log files.**
			Server for schedule
Element	Code	Note	log files	Subdirectory

Arecibo	AR	*	ftp.naic.edu	/pub/ast/vlbi/
ATCA (Narrabri)	AT	*	ftp.atnf.csiro.au	/pub/people/vlbi/vsop/logs/mmmyy
Bear Lakes	BL	*	vlbeer.ira.bo.cnr.it	vlbi_arch/mmmyy
Ceduna	CD	*	ftp.atnf.csiro.au	/pub/people/vlbi/vsop/logs/mmmyy
Effelsberg	EB		aspen.aoc.nrao.edu	astronomy/mmmyy/
Goldstone	GO		lilypad.jpl.nasa.gov	/pub/vlbiscpr/mmmyy
Green Bank	GB	*	aspen.aoc.nrao.edu	astronomy/mmmyy/
Hartebeesthoek	HH	*	ftp.atnf.csiro.au	/pub/people/vlbi/vsop/logs/mmmyy
Hobart	HO	*	ftp.atnf.csiro.au	/pub/people/vlbi/vsop/logs/mmmyy
Jodrell Bank	JB		vlbeer.ira.bo.cnr.it	vlbi_arch/mmmyy
Kalyazin	KL	*	vlbeer.ira.bo.cnr.it	vlbi_arch/mmmyy
Kashima	KA	*	hotaka.mtk.nao.ac.jp	mmmyy
Medicina	MC		vlbeer.ira.bo.cnr.it	vlbi_arch/mmmyy
Metsahovi	MH		vlbeer.ira.bo.cnr.it	vlbi_arch/mmmyy
Mopra	MO	*	ftp.atnf.csiro.au	/pub/people/vlbi/vsop/logs/mmmyy
	also:		sgra.jpl.nasa.gov	/pub/users/tingay/mopratsys
Noto	NT	*	vlbeer.ira.bo.cnr.it	vlbi_arch/mmmyy
Onsala	ON		vlbeer.ira.bo.cnr.it	vlbi_arch/mmmyy
Robledo	RO		lilypad.jpl.nasa.gov	/pub/vlbiscpr/mmmyy
Shanghai	SH	*	vlbeer.ira.bo.cnr.it	vlbi_arch/mmmyy
Tidbinbilla (MkIV and S2 pre-May 1999)	TI	*	lilypad.jpl.nasa.gov	/pub/vlbiscpr/mmmyy
Tidbinbilla (S2 from May 1999)	TI	*	ftp.atnf.csiro.au	/pub/people/vlbi/vsop/logs/mmmyy
Torun	TR		vlbeer.ira.bo.cnr.it	vlbi_arch/mmmyy
Usuda	UD	*	hotaka.mtk.nao.ac.jp	mmmyy See also below!
VLA-27	Y		aspen.aoc.nrao.edu	astronomy/mmmyy/
VLBA	VLBA		aspen.aoc.nrao.edu	astronomy/mmmyy/
WSRT	WB		vlbeer.ira.bo.cnr.it	vlbi_arch/mmmyy

Note: * signifies that nominal Tsys and/or gain information for this telescope is available further down this page.

**Mission Element FTP Sites**
Site	Host Name	IP Address	Account
EVN Regional Server	vlbeer.ira.bo.cnr.it	192.167.165.196	evn (*)
VLBA Regional Server	aspen.aoc.nrao.edu	146.88.5.8	vlbiobs (*)
Mitaka Regional Server	hotaka.mtk.nao.ac.jp	133.40.7.35	vlbi (*)
ATNF Regional Server	ftp.atnf.csiro.au	130.155.194.32	anonymous
DSN 70m Regional Server	lilypad.jpl.nasa.gov	137.79.62.111	anonymous (**)
Arecibo server	ftp.naic.edu	192.65.176.4	anonymous

(*) indicates that a password is needed to gain access to these accounts. These may be obtained on request. Passwords should not be exchanged by electronic means.

(**) indicates that a user's IP address must be registered with the router used for accessing lilypad.

Gain Curves

Accessing gain curve data for the VLBA and VLA is described in the memo (link is disconnected) which is e-mailed to PIs after their observation. The ANTAB files prepared by the EVN have the gain curve information included in them -- see the next section. Details for other telescopes will be added soon.

Phase Calibration Tones

Not all telescopes can measure phase calibration tones. HALCA does insert phase calibration tones, and these are extracted at the tracking stations. More information on these will be available in the near future. The main use of the phase calibration tones is to combine the two channels. For GRTs this can normally be done using data from a scheduled fringe finder or calibrator source.

Nominal Tsys and Gain Information

In some cases, only nominal antenna calibration information is available. Nominal system temperature and gain information, in ANTAB format, for Arecibo, ATCA, Ceduna, Tidbinbilla (DSS43), Hartebeesthoek, Hobart, Kashima, Mopra, Noto, NRAO Green Bank 140ft, Shanghai and Usuda are available in the following files:

1.6 GHz	5 GHz
nominal_gain_L.cal nominal_tsys_L.cal	nominal_gain_C.cal nominal_tsys_C.cal

One step better than using the nominal Tsys values is to take into account the elevation dependence. The script which was available for generating nominal Tsys values suitable for AIPS input based on Tsys vs Elevation data has been disabled at present. 1.6GHz Tidbinbilla and 5GHz Ceduna data were available -- if there is sufficient demand, the script will be restored and information for more telescopes will be added. The script required the date and time of the observation and the source coordinates and used a polynomial fit to Tsys vs Elevation (or Tsys vs ZA) and the Antenna's DPFU to generate the Tsys values.

Usuda Tsys measurements are now available in a single file covering all experiments. Note all 5GHz observations appear first, followed by 1.6GHz observations. These will shortly be added to the Mitaka ftp site in one file per experiment in the mmmyy directory structure.

Please note that the gain for the ATCA depends on the number of antennas in the phased array during your experiment. Therefore, you will need to edit the ATCA entrys in nominal_gain_L.cal or nominal_gain_C.cal acordingly.

Thanks to Jim Lovell, Bill Scott, Steven Tingay, Misha Popov, Kenta Fujisawa and Kobayashi-san for their help in compiling this information.