Photometry

For photometry data all that is required after extinction/remsky is that the jiggle pattern be processed to determine the signal for each integration and bolometer. It is possible to derive the signal by taking the AVERAGE of the jiggle data or by fitting a PARABOLA to the data. Parabola fitting probably should not be used unless the sky was exceptionally stable - the individual jiggle maps rarely look like they can be fitted by a parabola.

For this example I will use photometry data on 3C279 taken just before the example used for mapping. The data have been processed in the same way as scan 59.

% scuphot n56_sky_lon
SURF: run 56 was a PHOTOM observation of 3c279
SURF: file contains data for 1 exposure(s) in 10 integrations(s) in 1
measurement(s)
ANALYSIS - Which reduction method /'AVERAGE'/ > 
OUT - Name of container file to hold map and time-sequence data > n56_pht_lon 
FILE - Name of ASCII file to contain results summary /!/ > n56.txt

In this example n56_sky_lon.sdf is processed with scuphot. This observation consisted of 10 integrations and used a 9-point jiggle pattern. The value of each integration was determined by taking the average of the jiggle pattern. In some cases a better signal-to-noise can be achieved by processing the individual two second samples rather than averaging over the nine samples that comprise an integration. For these cases, usually short observations, where the scatter on the averaged data is not representative of the standard deviation of the raw data (small number statistics) ANALYSIS=SAMPLE is recommended.

Information on samples or integrations is written to a text file (n56.txt in this case) and also to n56_pht_lon.sdf. Since photometry observations can use multiple bolometers n56_pht_lon.sdf is in fact a HDS container [21] which contains two NDFs per bolometer: $<$BOL$>$_peak contains the photometry data for each integration and $<$BOL$>$_map contains the integrated jiggle pattern (assuming the jiggle pattern was on a regular grid - irregular jiggle patterns are written as 1-D images and no map is written for zero offset jiggles). In this example the bolometer used was H7 so that n56_pht_lon.h7_peak would be the NDF containing the integration data (the ascii version of which can be found in n56.txt) and n56_phot_lon.h7_map which would contain the integrated jiggle pattern

Since many photometry observations are usually combined to give the final result the scucat task can be used to concatenate data files that have been produced with scuphot (scucat knows about the _peak NDFs). In this case we have combined the three photometry observations listed in §:

% scucat 
METHOD - Concatenation method /'SEPARATE'/ > 
OUT - Rootname of files to contain concatenated data > 3c279
IN - Name of input file containing photometry data /'n56_pht_lon'/ >
SURF: Found data for the following bolometers: h7
SURF: This is a PHOTOM observation of 3c279. There are 10 integrations
IN - Name of input file containing photometry data /!/ > n57_pht_lon
SURF: Found data for the following bolometers: h7
SURF: This is a PHOTOM observation of 3c279. There are 10 integrations
IN - Name of input file containing photometry data /!/ > n58_pht_lon
SURF: Found data for the following bolometers: h7
SURF: This is a PHOTOM observation of 3c279. There are 10 integrations
IN - Name of input file containing photometry data /!/ >

scucat continues to request input data until a null value (!) is given for the IN parameter. Since different bolometers should be processed independently, a new file is created for each bolometer. In this example scucat produces one file called 3c279_h7.sdf; if this data was taken with 2-bolometer chopping there would have been another file called 3c279_h9.sdf (for example). These files can now be analysed with standard statistics packages (e.g. KAPPA stats and kstest).

An alternative to the above for scucat is to use a text file to contain the list of filenames to be processed (useful for scripts):

% scucat noloop
METHOD - Concatenation method /'SEPARATE'/ > 
OUT - Rootname of files to contain concatenated data > 3c279
IN - Name of input file containing photometry data /'n56_pht_lon'/ > ^in.lis
SURF: Found data for the following bolometers: h7
SURF: This is a PHOTOM observation of 3c279. There are 10 integrations
SURF: Found data for the following bolometers: h7
SURF: This is a PHOTOM observation of 3c279. There are 10 integrations
SURF: Found data for the following bolometers: h7
SURF: This is a PHOTOM observation of 3c279. There are 10 integrations

where in.lis contains the names of the 3 filenames to be processed (a comma separated list is also allowed).

If you do not want to process different bolometers independently, the METHOD parameter can be set to CATALL, in which case all data will be concatenated together regardless of bolometer and the output filename will match that specified in OUT (rather than being OUT + bolometer name).