TIFR GMRT Sky Survey (TGSS)
S. K. Sirothia, N. G. Kantharia, C. H. Ishwara-Chandra, Gopal-Krishna
NCRA-TIFR, Pune, India
Test Data Analysis
An optimised observing strategy was arrived upon by
conducting several experiments using test time awarded on GMRT.
There were three main aspects which were explored. First was to
do with the settings, the second was do with the differences in the day and night
observing and the third was to do an optimum sky coverage for each pointing.
Same fields were observed on three consecutive days, with the same configuration
and settings except the ALC (automatic Level Control) being included or excluded
from the signal path and the IF and baseband bandwidths.
The results of this experiment are shown in the figure below.
This figure is taken from a talk given by S.K.Sirothia
It is clear that the data obtained with the ALC on and with a 16 MHz
IF bandwidth gives the best results and this is what we adopt for the survey.
Comparing the results from nighttime and daytime observing.
We compared the images obtained using data taken in the day time with the images
from the data taken in the night time.
We find that on the average the images made from the data acquired in the night time
is better by a factor of about 1.5. We have requested GTAC and the
Observatory to schedule our observing in the night time.
We compared the results of different sky coverages. Each pointing at a given
HA is observed for 3.5m. We compared the images made from data over 3 HAs
with data over 5 HAs. The results obtained using data over
5 HAs were clearly better and this is used in our survey.
Last updated: 30 April 2010