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: http://www.naic.edu/~astro/obsmodes.shtml
Дата изменения: Unknown Дата индексирования: Mon Oct 1 21:58:01 2012 Кодировка: Поисковые слова: trifid nebula |
This page shows which observing modes are available with which correlator and gives a brief description of the observing modes..
• – available;
* – available but not recommended;
- – not available.
| Mode (spectral line) |
Interim Correlator |
WAPP Single Pixel |
WAPP ALFA |
|
|---|---|---|---|---|
| Cal spider scan | • | - | - | Calibration mode that scans 4 times across the calibrator, forming a ‘spider’ shape. |
| Cal cross scan | • | - | - | Calibration mode that scans twice across the calibrator, forming a cross shape. |
| Run correlator | • | • | • | Takes data – whatever the telescope is doing. |
| Cross scan | • | - | - | Scans twice across the target, forming a cross shape. |
| Standard on | • | • | • | Takes data pointing at the source position. |
| Standard on/off | • | • | • | Takes data alternately at the source position and an ‘off’ position that tracks the same Az and ZA across the dish to give a baseline. This is the standard spectral-line single-pixel observing mode. |
| Ephemeris tracking | • | • | • | Takes data while tracking a source from an ephemeris. |
| Drift map | • | • | • | Takes data while the telescope is stationary, thus building up sky coverage as the sky rotates. |
| RA/Dec map | • | • | • | Actively scan the sky to build up coverage of an area. This provides significantly poorer baselines than drift scanning. |
| Double position switching | • | • | • | Switches between the target, its off-beam, a nearby continuum source, and its off-beam. This provides good bandpass calibration for targets that are strong continuum sources. |
| Hex map | • | - | - | Does a center position and 6 evenly spaced hexagonal position around it in various patters. Not implemented in CIMA |
| WAPP cross map | - | • | * | As for the ‘cross scan’ mode, but using the WAPP backend. |
| ALFA cross map | - | * | • | Makes a cross map (as above) for any or every ALFA beam. |
| Leapfrog map | - | • | • | ALFA mapping mode that ‘leapfrogs’ across the sky so that each set of observations forms the off-beam (as for standard on/off) for the previous observation. |
| Alternative drift map | - | • | • | An alternative drift-scanning mode which starts drifting at a specified LST. |
| Fixed azimuth drift map | - | • | • | The standard drift-scanning mode for ALFA, used by the ALFALFA and AGES extragalactic surveys, where the telescope starts taking data when a specified position (in sky coordinates) reaches a specified azimuth.. |
| Basketweave scanning | - | • | • | An active scanning mode where the telescope is held on the meridian and driven in zenith. This is used by the Galactic ALFA surveys. |
| Smart frequency switching | - | • | • | A Calibration mode used by the Galactic ALFA surveys to calibration the G-ALFA HI Spectrometer. |
| Drift chase map | - | * | • | A modified drift-scanning mode where three beams of ALFA are aligned to give very deep coverage. This is used by the AUDS extragalactic survey. |
| Mode (pulsar) |
WAPP Single Pixel |
WAPP ALFA |
|
|---|---|---|---|
| Standard on | • | • | Takes data pointing at the source position. |
| Pulsar calibration script | • | - | Points four beamwidths away from the pulsar and turs on the 25Hz cal for 10s, then points at the pulsar and turns the cal on for 10s. |
| Continuum calibration script | • | - | Goes to a continuum calibration source and fires the 25Hz cal, then repeats this away from the source. |
| ALFA beam check | - | • | Observes a bright test pulsar for 67 seconds with each ALFA beam to test that all beams are working and have good sensitivities and that the pointing is accurate. |
| ALFA calibration check | - | • | Takes data with the cal on and all beams away from source then points each beam in turn at a calibrator source. |
| WAPP ZA scanning mode | • | • | ??? |
| WAPP Az/ZA mapping mode | • | • | Maps the sky, scanning actively in Az and ZA. |
| WAPP RA/Dec mapping mode | • | • | Maps with active scanning in RA and Dec. |
| WAPP Gal-l/b mapping mode | • | • | Maps with active scanning in l and b. |
Note: Automation of ALFA rotation to provide either the same sky-angle or an even declination spacing of the beams is available. users of this should bear in mind that even if the ALFA sky angle is kept fixed, the outer beams will move as the geometry of the system changes.