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Next: 8.3 Common Processing Steps Up: 8. Data Processing Level: Previous: 8.1 Overview

Subsections


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 by the satellite.

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:
    1. Average source power and off-source background(s) power
      Staring mode
      No action required.
      Chopped mode
      Determine source power, step 8.4.1

    2. If point source was indicated by observer:
      1. Convert power to flux density
        Photometry step 8.4.6.
      2. Write PHT-P point source photometry product
        Photometry step 8.4.8.
    3. If extended source was indicated by observer:
      1. Convert power to flux density
        Photometry step 8.4.6.
      2. Convert flux density to surface brightness
        Photometry step 8.4.7;
      3. Write PHT-P extended source photometry product
        Photometry step 8.4.9.
  4. If raster mapping performed:
    1. Determine celestial coordinates of detector origin and centre;
      loop over all measurements in AOT
      Common step 8.3.3;
    2. For each record, convert power to surface brightness
      Photometry step 8.4.7;
    3. Produce photometric image
      Mapping steps 8.5.2 to 8.5.5;
    4. Write raster map products 8.5.6;
    5. Write PHT-P raster scan photometry product
      Mapping step 8.5.7.


8.2.2 PHT04

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
    Determine source power, step 8.4.1
  4. If point source indicated by observer:
    1. Convert power to flux density
      Photometry step 8.4.6.
    2. Write PHT-P point source photometry product
      Photometry step 8.4.8.
  5. If extended source indicated by observer:
    1. Convert power to flux density
      Photometry step 8.4.6;
    2. Convert flux density to surface brightness
      Photometry step 8.4.7;
    3. Write PHT-P extended source photometry product
      Photometry step 8.4.9.


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 was indicated by observer:
    1. Convert power to flux density
      Photometry step 8.4.6.
    2. Write PHT-P point source photometry product
      Photometry step 8.4.8.
  4. If extended source was indicated by observer:
    1. Convert power to flux density
      Photometry step 8.4.6.
    2. Convert flux density to surface brightness
      Photometry step 8.4.7;
    3. Write PHT-P extended source photometry product
      Photometry step 8.4.9.


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
    1. Read SPD Header
      Common step 8.3.1.
    2. Read SPD record
      Common step 8.3.2.
  2. If last product was found then loop over all measurements read:
    1. If point source was indicated by observer:
      1. Convert power to flux density
        Photometry step 8.4.6.
      2. Write PHT-P point source photometry product
        Photometry step 8.4.8.
    2. If extended source was indicated by observer:
      1. Convert power to flux density
        Photometry step 8.4.6.
      2. Convert flux density to surface brightness
        Photometry step 8.4.7;
      3. Write PHT-P extended source photometry product
        Photometry step 8.4.9.


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.

Processing steps:

  1. Read SPD Header
    Common step 8.3.1.
  2. Read SPD record
    Common step 8.3.2.
  3. If single pointing:
    1. Average source power and off-source background(s) power
      This step is applied to each pixel.
      Staring mode
      No action required.
      Chopped mode
      Determine source power, step 8.4.1
    2. Summation of powers in array, step 8.4.2
    3. If point source was indicated by observer:
      1. Determine Gaussian parameters
        Interpolation: 
        Interpolate missing pixels
        Photometry step 8.4.4;
        Fitting: 
        Determine source peak and position
        Photometry step 8.4.5;
      2. Convert power to flux density
        Photometry step 8.4.6;
      3. Write PHT-C point source photometry product
        Photometry step 8.4.10.
    4. If extended source was indicated by observer:
      1. Convert power to flux density
        Photometry step 8.4.6;
      2. Convert flux density to surface brightness
        Photometry step 8.4.7;
      3. Write PHT-C extended source photometry product
        Photometry step 8.4.11.
  4. If raster mapping performed:
    1. Determine celestial coordinates of each detector pixel for each record;
      loop over all measurements
      Common step 8.3.3;
    2. For each record and pixel, convert power to flux density
      Photometry step 8.4.6;
    3. For each record and pixel, convert flux density to surface brightness
      Photometry step 8.4.7;
    4. Produce photometric image
      Mapping steps 8.5.1 to 8.5.5;
    5. Write raster map products
      Mapping step 8.5.6.
    6. Write PHT-C raster scan photometry product
      Mapping step 8.5.8.


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 was indicated by observer:
    1. Summation of powers in array, step 8.4.2
    2. Determine Gaussian parameters
      Interpolation: 
      Interpolate missing pixels
      Photometry step 8.4.4;
      Fitting: 
      Determine source peak and position
      Photometry step 8.4.5;
    3. Convert power to flux density
      Photometry step 8.4.6.
    4. Write PHT-C point source photometry product
      Photometry step 8.4.10.
  4. If extended source was indicated by observer
    1. Convert power to flux density
      Photometry step 8.4.6.
    2. Convert flux density to surface brightness
      Photometry step 8.4.7;
    3. Write extended source photometry product
      Photometry step 8.4.11.


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.

Processing steps:

  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 8.4.6;
  5. For each record and pixel, convert flux density to surface brightness
    Photometry step 8.4.7;
  6. Produce photometric image
    Mapping steps 8.5.1 to 8.5.5;
  7. Write raster map products
    Mapping step 8.5.6.
  8. Write PHT-C raster scan photometry product
    Mapping step 8.5.8.


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.

Processing steps:

  1. Loop over all PHT37, PHT38. . ., PHT39 of the same TDT
    1. Read SPD Header
      Common step 8.3.1.
    2. Read SPD record
      Common step 8.3.2.
  2. If last product was found then loop over all measurements read:
    1. If point source was indicated by observer:
      1. Convert power to flux density
        Photometry step 8.4.6.
      2. Write PHT-C point source photometry product
        Photometry step 8.4.10.
    2. If extended source was indicated by observer:
      1. Convert power to flux density
        Photometry step 8.4.6.
      2. Convert flux density to surface brightness
        Photometry step 8.4.7;
      3. Write PHT-C extended source photometry product
        Photometry step 8.4.11.


8.2.9 PHT40

Spectrophotometry with the PHT-S subsystem. Staring, 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:
    1. If point source was indicated by observer:
      1. Determine point source spectrum $F_{\lambda}(i)$: step 8.6.1
      2. Write point source spectroscopy product
        Spectroscopy step 8.6.3.
    2. If extended source was indicated by observer:
      1. Determine surface brightness spectrum $F_{\lambda}(i)$: step 8.6.2
      2. Write extended source spectroscopy product
        Spectroscopy step 8.6.3.
  4. If raster mapping performed:
    1. Determine celestial coordinates of each raster point:
      loop over all raster points in AOT
      Common step 8.3.3.
    2. For each raster point $j$, determine surface brightness spectrum $F_{\lambda}(i,j)$:
      step 8.6.2.
    3. Write raster map product:
      Spectroscopy step 8.6.3.

For raster observations no images are produced. For each raster pointing a record containing a spectrum plus the associated coordinates area are written to the product.

next up previous contents index
Next: 8.3 Common Processing Steps Up: 8. Data Processing Level: Previous: 8.1 Overview
ISO Handbook Volume IV (PHT), Version 2.0.1, SAI/1999-069/Dc