Observing Spectral Lines

News:

• Event Log(staff only)
• Status updates: Receivers, ACSIS

An Introduction to Heterodyne Observing at the JCMT:

• Spectral Line Observing guide: A guide for new ( and not so new ) users.
  Covers basic concepts, techniques, calibration (for more recent results see the links below) and data reduction. Note that this has not yet been updated for observing with ACSIS.
  HTML and postscript.
• Configuring a heterodyne Science Program: the JCMT Observing Tool

Spectral Line Receivers - "Front ends":

• HARP-B: 345 GHz, 16-pixel array receiver - general description and details
• Receiver A3: 230 GHz, single-pixel DSB receiver - general description and details
• Receiver W: 345 and 690 GHz, dual-polarisation DSB/SSB receiver - see also general description and details
• Receiver B3 (Retired): 345 GHz, dual-polarisation DSB/SSB receiver
• Heterodyne polarimeter (Not currently available): Rover will be offered with ACSIS after commissioning.

Spectrometer - "Back ends":

• The ACSIS digital autocorrelation spectrometer is used as the backend for available spectral line receivers.
  • Currently available observing modes
  • Special ACSIS setup configurations for the spectrometer to handle some special circumstances.
• The DAS has been retired from the JCMT.
  A description of the Digital Autocorrelation Spectrometer can be found here or as a Postscript file.

Spectral Line Frequencies:

• List of all molecular species currently known in space - by Al Wootten
• JPL spectral line catalog browser form; and explanation of use
• List of observed microwave lines (Lovas 2002 revision); see also NIST fundamental data listings
• The Cologne Database for Molecular Spectroscopy

Heterodyne Integration Time Calculator:

• HITEC - a web-based tool for calculating required integration times for heterodyne observations.
• Instructions for use.

Spectral Line Data Reduction:

• Spectral-Line Pipeline Reduction Scripts (under construction!), the orac-dr reduction facility, and how to configure orac_dr for ACSIS data(to be written!).
• ACSIS:
  • Cookbook. We welcome feedback on how we can improve the information given within.
  • Quick guide.
  • Starlink software. The reduction of ACSIS data is done using the STARLINK package.
    • Download the latest version of the STARLINK.
    • release notes.
• DAS (retired):
  • GSD data format: the DAS spectral line data format.
  • SPECX (retired): DAS datareduction software, still used for reduction of archived DAS data.
    • Download SPECX.
    • SPECX Cookbook (Postscript).
    • Crash Course in SPECX, for those in a hurry.
    • Full SPECX manual ((postscript)
    • Introduction to velocity and frequency scales in SPECX (courtesy Andy Gibb) - 160Kb
• CLASS: One can also use CLASS for the reduction of DAS data, and for ACSIS data (but some header parameters are missing)

Comparison Spectra and Telescope Efficiencies:

• Observations of a number standard sources at frequently-observed lines are used to verify system performance during observing.
  • Average spectra: These are available for HARP and RxA3, and are the average of spectra observed with the ACSIS backend under variable conditions, but judged to be of acceptable quality.
  • In ACSIS Current Calibrations are listed for RxA3 and HARP the results of observations towards standard sources, as well as beam efficiencies derived from planet observations (for the moment only for HARP). The average spectra were obtained from these observations.

• Planetary flux data can also be used for calibration.

• Older measurements and utilities that may still be useful:
  • Standard Spectra: These typically were taken with the DAS backend under controlled conditions during a special campaign several years ago . Although of good quality, systematic differences with newer receivers warrant caution. All receivers used have been retired since: B3, A2, B3i, and C2.
  • Representative spectra: These were also taken a few years ago and aimed to complement the standard spectra by adding data on non-standard, but frequently used frequencies. They were selected by hand as deemed 'representative', at a time that averaging large numbers of spectra was not common practice. Some frequencies are not very representative due to a lack of data. All receiver used have been retired or upgraded since: A3, B3, WC and WD
  • A web interface to our (DAS) standard spectra database is available, as is an interface to the (DAS) efficiencies database. In these databases are all observations of standard sources and planets, and derived aperture and beam efficiencies (main beam efficiency for Uranus and Neptune, and for Mars, when its diameter is small) .
  • Results of Moon measurements and derived Moon efficiencies are given here.
  • For archival DAS data, one can use the plot-standard command inside SPECX to see how an observation of a standard source compares with the true "standard", if a standard spectrum is available.

Velocity Considerations:

• Velocity frames and definitions
• You can calculate the LSR Velocity to see if the telluric line might interfere with your observation if you are doing frequency switching (use topocenctric velocity for IAU Standard Solar Motion and multiply velocity with -1.0).
• Velocity & frequency scales; identifying image band lines (within SPECX), (Andy Gibb, 2004)

Heterodyne Beam Map Archive: beam maps made with the heterodyne instruments

Atmospheric Transmission: check actual amount of water vapor at your observing frequency.

Special Techniques: Spectral line fivepoints and focus observations.

Staff wiki: - password protected: current performance, instructions, troubleshooting