vishead - A new task for CASA

News

I have implemented a vishead prototype task. Presently, it only lists data using the ms.summary() method. I would like some feedback before I go further.

Questions

• What is the purpose of this task? How does it compare to listobs and ms.summary() ?
• How do I handle data that varies throughout the MS? For example, observing frequency can change even for the same source.
• Do we want to list subtable information, the way AIPS lists table info (CL table, etc.)?

Desired vishead output

Data unique throughout MS:

Datum	vishead Keyword	FITS Keyword	Origin in MS
MS filename	msname		(from input parameter)
telescope	telescope	TELESCOP or INSTRUME	ms:observation:telescope_name
receiver	?	?
observer	observer	OBSERVER	ms:observation:observer
observ. date	date_obs	DATE_OBS	ms:observation:time_range
project	project	?	ms:observation:project
MS creation date	msdate	DATE	(from filesystem: date created)
# visibilities	nvis	NAXISn	(Calulate: ms.nrow() * N_c * N_f)
Coord equinox	equinox	EQUINOX	?
Velocity definition (optical or radio)	veldef		ms:doppler:veldef

Data that may vary throughout MS:

Object	object	OBJECT	?
Frequencies
Polarizations
Rest frequency
Velocity restframe (heliocentric, lsr, ...)
Velocity reference value and reference pixel

-- JaredCrossley - 10 Nov 2008