Next: 8.3 Common processing steps Up: 8 Data Processing Level: Previous: 8.1 Overview

8.2 PHT auto analysis processing per AOT

No description is given of the polarisation AOTs PHT50 and PHT51 because these AOTs are not included in the pipeline SPD and AAR levels.

8.2.1 PHT03

This AOT performs photometry in user-selected wavebands using the PHT-P subinstrument, with either the staring or chopping mode. If the staring mode is selected a raster scan may be performed.

The description of the processing required for rasters is incorporated, since the same steps are required to process measurements at each raster position.

Processing steps:

1.

Read SPD Header
Common step 8.3.1.

2.

Read SPD record
Common step 8.3.2.

3.

If single pointing:

(a)

Average source power and off-source background(s) power

Staring mode: No action required.
Chopped mode: Photometry step 8.4.2.
Obtain mean powers averaged over all valid chopper cycles.
Apply empirical signal difference correction 8.4.6.

(b)

If point source observed:

i.: Convert power to flux density
Photometry step 8.4.9.
ii.: Write point source photometry product
Photometry step 8.4.11.

(c)

If extended source observed:

i.: Convert power to flux density
Photometry step 8.4.9.
ii.: Convert flux density to surface brightness
Photometry step 8.4.10;
iii.: Write extended source or raster photometry product
Photometry step 8.4.12.

4.

If raster mapping performed:

(a): Determine celestial coordinates of detector origin and centre; loop over all measurements in AOT
Common step 8.3.3;
(b): For each record, convert power to surface brightness
Photometry step 8.4.10;
(c): Produce photometric image
All mapping steps 8.5;
(d): Write raster map products 8.5.5.

This AOT performs multi-aperture photometry with a single user-selected filter at one sky position using the PHT-P subinstrument. The focal plane chopper may be operated in either staring or chopping mode. Raster scans may not be selected.

Processing steps:

1.

Read SPD Header
Common step 8.3.1.

2.

Read SPD record
Common step 8.3.2.

3.

Average source power and off-source background(s) power

Staring mode: No action required.
Chopped mode: Photometry step 8.4.2.
Obtain mean powers averaged over all valid chopper cycles.
Apply empirical signal difference correction 8.4.6.

4.

If point source observed:

(a): Convert power to flux density
Photometry step 8.4.9.
(b): Write point source photometry product
Photometry step 8.4.11.

5.

If extended source observed:

(a): Convert power to flux density
Photometry step 8.4.9;
(b): Convert flux density to surface brightness
Photometry step 8.4.10;
(c): Write extended source or raster photometry product
Photometry step 8.4.12.

8.2.3 PHT05

This AOT performs absolute photometry of the sky brightness with a single filter/aperture combination at one sky position using the PHT-P subinstrument. Raster scans cannot be selected.

Processing steps:

1.

Read SPD Header
Common step 8.3.1.

2.

Read SPD record
Common step 8.3.2.

3.

If point source observed:

(a): Convert power to flux density
Photometry step 8.4.9.
(b): Write point source photometry product
Photometry step 8.4.11.

4.

If extended source observed:

(a): Convert power to flux density
Photometry step 8.4.9.
(b): Convert flux density to surface brightness
Photometry step 8.4.10;
(c): Write extended source or raster photometry product
Photometry step 8.4.12.

8.2.4 PHT17/18/19

These AOTs perform photometry in user-selected wavebands with a single user-selected aperture as part of a sparse map using the PHT-P subinstrument. Only staring mode can be used. The following processing steps are performed:

Processing steps:

1.

Loop over all PHT17, PHT18. . ., PHT19 of the same TDT

(a): Read SPD Header
Common step 8.3.1.
(b): Read SPD record
Common step 8.3.2.

2.

If last product was found then loop over all measurements read:

(a)

If point source observed:

i.: Convert power to flux density
Photometry step 8.4.9.
ii.: Write point source photometry product
Photometry step 8.4.11.

(b)

If extended source observed:

i.: Convert power to surface brightness
Photometry step 8.4.10;
ii.: Write extended source or raster photometry product
Photometry step 8.4.12.

8.2.5 PHT22

This AOT performs photometry in user-selected wavebands using the PHT-C subinstrument, with either the staring or chopping mode. If the staring mode is selected a raster scan may be performed.

1.

Read SPD Header
Common step 8.3.1.

2.

Read SPD record
Common step 8.3.2.

3.

If single pointing:

(a)

Average source power and off-source background(s) power
This step is applied to each pixel.

Staring mode: No action required.
Chopped mode: Photometry step 8.4.2.
Obtain mean powers per pixel averaged over all valid chopper cycles.
Apply empirical signal difference correction 8.4.6.

(b)

Determine mean off-source background power over all pixels
Photometry step 8.4.5.

(c)

Summation of powers in array, step 8.4.7

(d)

If point source observed:

i.

Determine Gaussian parameters

Interpolation:: Interpolate missing pixels
Photometry step 8.4.8.1;
Fitting:: Determine source peak and position
Photometry step 8.4.8.2;

ii.

Convert power to flux density
Photometry step 8.4.9;

iii.

Write point source photometry product
Photometry step 8.4.13.

(e)

If extended source observed:

i.: Convert power to flux density
Photometry step 8.4.9;
ii.: Convert flux density to surface brightness
Photometry step 8.4.10;
iii.: Write extended source or raster photometry product
Photometry step 8.4.14.

4.

If raster mapping performed:

(a): Determine celestial coordinates of each detector pixel for each record; loop over all measurements
Common step 8.3.3;
(b): For each record and pixel, convert power to flux density
Photometry step 8.4.9;
(c): For each record and pixel, convert flux density to surface brightness
Photometry step 8.4.10;
(d): Produce photometric image
All mapping steps 8.5;
(e): Write raster map products 8.5.5.

8.2.6 PHT25

This AOT performs absolute photometry of the sky brightness with a single filter on one sky position using the PHT-C subinstrument. Raster scans cannot be selected, only staring mode is available.

Processing steps:

1.

Read SPD Header
Common step 8.3.1.

2.

Read SPD record
Common step 8.3.2.

3.

If point source observed:

(a)

Summation of powers in array, step 8.4.7

(b)

Determine Gaussian parameters

Interpolation:: Interpolate missing pixels
Photometry step 8.4.8.1;
Fitting:: Determine source peak and position
Photometry step 8.4.8.2;

(c)

Convert power to flux density
Photometry step 8.4.9.

(d)

Write point source photometry product
Photometry step 8.4.13.

4.

If extended source observed:

(a): Convert power to flux density
Photometry step 8.4.9.
(b): Convert flux density to surface brightness
Photometry step 8.4.10;
(c): Write extended source photometry product
Photometry step 8.4.14.

8.2.7 PHT32

This AOT performs multi-filter mapping using either the C100 or C200 arrays. The map may take the form of a linear scan. A raster scan is performed; the focal plane chopper being used to sample at intermediate positions from the raster pointings in sawtooth mode.

1.: Read SPD Header
Common step 8.3.1.
2.: Read SPD record
Common step 8.3.2.
3.: Determine celestial coordinates of each detector pixel for each record; loop over all measurements
Common step 8.3.3;
4.: For each record and pixel, convert power to flux density
Photometry step 8.4.9;
5.: For each record and pixel, convert flux density to surface brightness
Photometry step 8.4.10;
6.: Produce photometric image
All mapping steps 8.5;
7.: Write raster map products 8.5.5.

8.2.8 PHT37/38/39

These AOTs perform photometry in user-selected wavebands as part of a sparse map using the PHT-C subinstrument. Only staring mode observations are performed.

1.

Loop over all PHT37, PHT38. . ., PHT39 of the same TDT

(a): Read SPD Header
Common step 8.3.1.
(b): Read SPD record
Common step 8.3.2.

2.

If last product was found then loop over all measurements read:

(a)

If point source observed:

i.: Convert power to flux density
Photometry step 8.4.9.
ii.: Write point source photometry product
Photometry step 8.4.13.

(b)

If extended source observed:

i.: Convert power to flux density
Photometry step 8.4.9.
ii.: Convert flux density to surface brightness
Photometry step 8.4.10;
iii.: Write extended source or raster photometry product
Photometry step 8.4.14.

8.2.9 PHT40

Spectrophotometry with the PHT-S subsystem. Staringg, chopped, and mapping modes are available. Point or extended sources can be observed. The short (SS) and the long (SL) wavelength detectors are processed separately.

Processing steps:

1.

Read SPD Header
Common step 8.3.1.

2.

Read SPD record
Common step 8.3.2.

3.

If single pointing:

(a)

Average source power and off-source background(s) power
This step is applied to each pixel.

Staring mode: No action required.
Chopped mode: Photometry step 8.4.2.
Obtain mean powers averaged over all valid chopper cycles.

(b)

If point source observed:

i.: Convert power to flux density
Photometry step 8.4.9.
ii.: Write point source photometry product
Photometry step 8.6.1.

(c)

If extended source observed:

i.: Convert power to surface brightness
Photometry step 8.4.10;
ii.: Write extended source or raster photometry product
Photometry step 8.6.1.

4.

If raster mapping performed:

(a): Determine celestial coordinates of each raster point; loop over all measurements in AOT
Common step 8.3.3;
(b): For each record, convert power to flux density
Photometry step 8.4.10;
(c): For each record, convert flux density to surface brightness
Photometry step 8.4.10;
(d): Write raster map products.

For raster observations no images are produced. For each raster pointing a photometry record plus associated coordinates are obtained.

Next: 8.3 Common processing steps Up: 8 Data Processing Level: Previous: 8.1 Overview

ISOPHOT Data Users Manual, Version 4.1, SAI/95-220/Dc