2.2. Photometer Launch Pad

2.2.1. Does the Photometer observation data need re-processing?

Inspecting your maps for possible problems is covered in SDRG Section 6.5.2.

In many cases, the photometer data is great straight out of the HSA, however, there may be occasions when reprocessing using the User pipeline scripts in HIPE may benefit your observation:

  • By using newer improved calibration files: to check the Calibration Tree version see the SDRG Section 5.2.

    Updating to a new Calibration Tree is described in the SDRG Section 5.4

  • If you see strange artefacts in the maps or bad quality maps in general (SDRG Section 6.5.2)

  • By improving already usable maps (e.g. baseline removal, destriping, adding turnarond data, e.g. see SDRG Section 6.8.1 )

2.2.2. Re-processing with the User Pipeline Scripts

This topic is covered in SDRG Section 6.5.1 for the Large Map and Parallel mode and SDRG Section 6.6.1 for the Small Map mode. The mapping pipeline flowchart is shown in SDRG Figure 6.34.

Simplified User Pipeline Scripts for re-processing SPIRE data are provided in HIPE:

  • Accessed directly from the Pipeline>SPIRE menu at the top of the HIPE window

  • Separate pipeline script for each observation mode

  • Include processing steps taking data from Level 0.5, through Level 1 to the final Level 2 maps

  • Final maps are saved as FITS files (not a pool) to any specified directory

  • The Observation Context can also be updated and saved to a new Pool (SDRG Section 6.5.1)

Line by line descriptions of the scripts with example plots are shown in SDRG SDRG Section 6.5.1, Section 6.6.1 .

The scripts assume the following;

  • The data is already on disk stored in a pool on your disk

  • The latest Calibration Tree is stored as a pool on your disk (to do this, see SDRG Chapter 5)

To run the User Scripts, 3 options must be set inside the script:

  • Observation ID, data pool name, output directory path (See SDRG Section 6.5.1 for other options)

Memory problems encountered during processing extremely large maps can be overcome by using a Temporal Pool (To do this, see SDRG Section 9.2)

From Level 0.5 to Level 1, the pipeline modules that users may with to experiment with are mainly:

  • If the observation has strong residual drifts the Recalculate Temperature Drifts module can be tried (see SDRG Section 6.5.2)

  • Deglitching algorithms (residual glitches are easily identifiable in the Error Maps)

  • In some circumstances the Signal Jump Identifier (see SDRG Section 6.5.2 )

  • In rare circumstances Low Pass Filter Correction (see SDRG Section 6.5.2)

From Level 1 to Level 2, the pipeline carries out an iterative Destriping process as default in order to remove low frequency noise. If problems are encountered in the final maps, the SPIRE pipeline offers alternatives to the this baseline removal:

  • Available from the Scripts > SPIRE Useful Scripts menu.

  • Median Baseline Removal (see SDRG Section 6.8.1)

  • Polynomial Baseline Removal (see SDRG Section 6.8.1)

Although the default Naïve mapper usually produces good maps, alternative mapping algorithms are also available (See SDRG Section 6.5.1.4).

For observations where producing maps of extended emission are the most important objective, additional Relative Gain Corrections are required to take into account the fact that all bolometers do not have the same uniform beam shape. This is set by an option in the SPIRE user pipeline ( SDRG Section 6.5.1.4)) The SPIA (SPIRE Photometer Interactive Analysis) package provides a structured GUI-based access to the more intricate parts of the scan map photometer pipeline and consists of tailored functions for I/O, Level 1, and Level 2 processing of SPIRE photometer scan map datasets (SPIA is described in SDRG Chapter 11)

2.2.3. Further Analysis

Source Extraction and Photometry is described in the SDRG Section 6.9.1

The Map Merging topic is described in the SDRG Section 6.11.3

Production of absolute calibrated maps for extended emission using the Planck zero-point correction is explained in the SDRG Section 6.10.1)

SPIRE astrometry is covered in the SDRG Section 6.11.4)

Treatment of Moving Object Maps is explained in the SDRG Section 6.12.1 and Section 6.12.2)

Various Post Pipeline analysis tools are available for SPIRE through HIPE. Users are also encouraged to read the Calibration chapter of the SPIRE Handbook (formerly the SPIRE Observers Manual).

  • Source extraction from SPIRE maps can be carried out using either the DAOphot or SussExtractor algorithms implemented within HIPE (SDRG Section 6.9.1.4)

  • A Timeline Source Fitter is available for source photometry from SPIRE timelines(described inSDRG Section 6.9.1.4). The current recommendation is to extract sources with one of the above algorithms and to carry out photometry at these positions using the timeline based fitter.

  • Aperture photometry can be performed by selecting an image in the Variables view and selecting annularSkyAperturePhotometry in the Tasks view. (SDRG Section 6.9.1.6)

  • The SDRG describes the recipes for aperture photometry of point sources and diffuse emission.

  • A Map Merging Script accessible from the Pipeline>SPIRE>Useful scripts menu can be used to merge the Level 1 timeline data from multiple observations (e.g. Parallel Mode, creating mosaics from many maps) to create a single map and output it as a FITS file (Section 6.11.3)

  • An Astrometry Correction script accessible from the Scripts > SPIRE Useful Scripts menu which allows SPIRE astrometry to be improved by aligning observations with eachother, ancilliary images or a source list (see SDRG Section 6.11.4)

  • Two Moving Object scripts accessible from the Scripts > SPIRE Useful Scripts menu are available to correct the maps for observations of moving objects to the moving object frame (see SDRG Section 6.12.1) and to identify the position of a faint moving object target in a map (see SDRG Section 6.12.2)

  • A Bolometer Finder script accessible from the Scripts > SPIRE Useful Scripts menu allows a User to click on a photometer map and to bring up a plot of the timelines of any bolometer crossing that map pixel. Useful for checking which bolometer timelines are responsible for map artifacts (see SDRG Section 8.3).

  • A Super Resolution Mapper script accessible from the Scripts > SPIRE Useful Scripts menu allows a User to create super resolution maps (see SDRG Section 6.11.5).