Interfacing Third-Party Instruments with the CSO Telescope

Hiroshige Yoshida
Caltech Submillimeter Observatory

1  Introduction

2  Interfaces

2.1  UIP-NET2

UIP-NET2 is a non-interactive UIP interface over the TCP/IP connection. It provides a visitor's instrument a total control over the CSO telescope.

2.1.1  Control of Telescope Thru UIP-NET2

Any legal UIP command can be issued thru UIP-NET2. However macros that take parameters like FAZO are not permitted. UIP-NET2 responds with a line containing a status code, followed by return values if any, terminated by CR+LF. Values are delimited by white space. A zero is returned as a status code if the command issued is semantically correct, otherwise a non-zero value is returned. A zero status value does "not" necessarily mean that an execution of the command was successful.

2.1.2  Status Information Available Thru UIP-NET2

Currently status information available thru UIP-NET2 is very limited. Commands for information not listed below can be added upon request. Latency for retrieving multiple information from the antenna computer thru this interface is very high.

• ACQUIRED_LIMITS - return acquisition limits for on- and off-sources
• GET AIRMASS - return current airmass

2.2  UIP-NET

UIP-NET is a network bridge to UIP similar to UIP-NET2 but has less user-friendly interface. It is used by SHARC II. Use of this interface for new development is not recommended.

2.3  PLOG

This is a proprietary binary data stream over TCP/IP, designed to deliver a limited number of "real-time" telescope information to a data acquisition computer.

• Modified Julian day at midnight (UTC)
• Time of day (0.01 s)
• 32-bit flags
• Local sidereal time (0.01 s)
• Requested apparent right ascension (0.01 s)
• Requested apparent declination (0.1 ^′′)
• Parallactic angle (0.1 ^′′)
• Offset in X (0.1 ^′′)
• Offset in Y (0.1 ^′′)
• Requested azimuth (0.1 ^′′)
• Requested elevation (0.1 ^′′)
• Error in azimuth (0.1 ^′′)
• Error in elevation (0.1 ^′′)

2.4  TELINFO

This is a Sun RPC (Remote Procedure Call) service over TCP/IP that provides "semi-static" telescope information to a third party instrument.

2.4.1  BOLOCAM Header (obsolete)

• Name of object
• Longitude-like coordinate of object
• Latitude-like coordinate of object
• Type of object coordinates
• Calendar year (UTC)
• Month (UTC)
• Day of month (UTC)
• Time at start (UTC)
• Sidereal time at start (LST)
• Sidereal time at end (LST)
• Mapping offset in X
• Mapping offset in Y
• Chopper throw
• Chopper frequency

2.4.2  SHARC II Header

• Modified Julian day at midnight (UTC)
• Day of year (UTC)
• UTC
• LST
• DUT1 (=UT1−UTC)
• DAT (=TAI−UTC)
• Source name
• Type of original source coordinates
• Right ascension
• Declination
• Epoch
• Galactic longitude
• Galactic latitude
• Azimuth
• Altitude
• (Apparent right ascension)
• (Apparent declination)
• Offset in right ascension (RAO)
• Offset in declination (DECO)
• Offset in Galactic longitude (GLO)
• Offset in Galactic latitude (GBO)
• Offset in azimuth (AZO)
• Offset in elevation (-ZAO)
• Mapping offset in right ascension (RAO/MAPPING)
• Mapping offset in declination (DECO/MAPPING)
• Field offset in right ascension (RAO/FIELD)
• Field offset in declination (DECO/FIELD)
• Mapping offset in Galactic longitude (GLO/MAPPING)
• Mapping offset in Galactic latitude (GBO/MAPPING)
• Mapping offset in azimuth (AZO/MAPPING)
• Mapping offset in elevation (-ZAO/MAPPING)
• Pointing file name
• Pointing constants
• T-term constants
• Alidade tilt toward the Side Cabin
• Alidade tilt toward the control room
• T-term offset in azimuth (TAZO)
• T-term offset in elevation (-TZAO)
• Fixed offset in azimuth (FAZO)
• Fixed offset in elevation (-FZAO)
• Tropospheric refraction
• Acquisition tolerance for "on" source
• Acquisition tolerance for "off" source
• Focus mode
• Secondary mirror position in X
• Secondary mirror position in Y
• Secondary mirror offset in Y
• Secondary mirror position in Z (focus)
• Secondary mirror offset in Z (focus)
• Secondary mirror position in θ
• Chopper throw
• Chopper frequency
• Chopper high window tolerance
• Chopper low window tolerance
• Chopping offset in azimuth (AZO/CHOPPING)
• (Instrument rotator mode)
• (Instrument rotator command position)
• (Instrument rotator encoder position)
• (Instrument rotator offset)
• Ambient temperature
• Relative humidity
• Barometric pressure
• (Peak wind speed)
• (Average wind speed)
• (Wind direction)
• (Epoch of wind information)
• Opacity at 225 GHz
• Uncertainty of opacity at 225 GHz
• Epoch of opacity at 225 GHz
• Opacity at 350 μm
• Uncertainty of opacity at 350 μm
• Epoch of opacity at 350 μm

2.4.3  Raster- & Drift-scan Parameters

• Scan length (^′′)
• Scan velocity (^′′ s⁻¹)
• Scan direction
• Scan offsets (^′′)
• Scan coordinates

2.4.4  Sweep Parameters

• Field size in X & Y
• Field offsets in X & Y
• Field direction
• Scan velocity
• Scan direction
• Type of field coordinates
• Phase offsets in X & Y
• Time offset
• "A" parameters
• "F" parameters
• Series length

2.5  Chicago Server

2.6  "TTL" Inputs & Outputs

3  Observing Modes

3.1  Sweep & Box-scan

These are observing modes developed for SHARC II but potentially useful for other millimeter- and submillimeter-instruments. They cause the telescope to constantly move on and around a target in Lissajous or "billiard-cushion" pattern. The telescope does not always "acquire" a commanded position, however.

3.2  Raster-scan & OTF Mapping

These cause the telescope to follow linear point-to-point trajectory on the sky. For applications position accuracy is important or raster-scan parameters are such that the telescope can not always catch up with a command position, PLOG should be used to associate exact position on the sky with data stream.

3.3  Drift-scan

This is a special raster-scan mode where a scan rate is equal to the sidereal rate. The end result is that the command position of the telescope is "stationary" wrt the horizontal coordinates of date and a target thus "drifts by" the telescope at the sidereal rate. It is not a true drift-scan mode since the drives are actively controlled to keep the telescope stationary. Tropospheric refraction and alidade tilt corrections are still applied in this mode.

3.4  Chicago Mode

3.5  UCB & Texas Modes

4  Case Studies

4.1  SHARC II

Major observing modes for SHARC II are SWEEP & BOX_SCAN where the telescope moves constantly on and around a target. TELINFO is used to obtain bulk of header information at the beginning of each observation. Information from PLOG and data stream are merged on the fly to associate each data frame with exact location on the sky it was taken. The telescope is usually controlled thru UIP interactively. UIP-NET is used to script special observing modes.

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File translated from T_EX by T_TH, version 4.03.
On 25 May 2012, 09:34.