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Following is the global methodology used for observations.
- The primaryflux density and bandpass calibrators used were
chosen from 3C48, 3C147 & 3C286.
At least one of these sources was often available in the sky at any given time
of observing.
- In each observation run about 5 to 10 sources were observed over the period of 5 to
8 hours. Typically, each source was observed for 17 to 20 minutes.
13 such observations were performed to observe all 150 sources.
- The primary/bandpass calibrator were observed after 1 to 2 hours of
observing of the target sources.
- The number of antennas available during any observing run ranged from 25 to
30.
- The observed flux/bandpass calibrator were used as a zeroth-order
secondary calibrator in the case of 235 MHz and 610 MHz data reduction.
We also assumed that the observed sources are themselves secondary calibrators, which
are bright enough (with steep spectra,
) and hence have
sufficient flux density to permit self-calibration at subsequent stage of data
reduction.
- The data could be corrupted due to RFI (Radio Frequency Interference),
hardware or software failures, power supply
failure, ionospheric scintillations, etc. Such data was flagged from the database
before it is was further used for analysis and subsequent mapping.
The gross flagging information was generated largely by monitoring the above sources of
errors caused during the observing runs.
Next: Data Reduction
Up: Observations
Previous: Receiver Settings
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Manisha Jangam
2007-06-19