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SPIRE


SPIRE Map-Making Test Campaign (2013)

Introduction

SPIRE Photometer is one of the key instruments on board of Herschel. Its legacy depends very much on how well the scanmap observations that it carried out during the Herschel mission can be converted to high quality maps. In order to have a comprehensive assessment on the current status of SPIRE map-making, as well as to provide guidance for future development of the SPIRE scan-map data reduction pipeline, we carried out a test campaign on SPIRE map-making in 2013.

Goals

  1. Compare the map-makers in the SPIRE pipeline with other mapmakers.
  2. In particular, identify the strengths and limitations of different mapmakers in dealing with the known SPIRE map-making issues, such as the cooler burp effect.
  3. Assess the resolution-enhancement capabilities of the super-resolution mappers, as compared to the destriper (the pipeline default), and investigate their applicability to various kinds of data as well as caveats or pitfalls to avoid.
  4. Enable users to choose the right map-maker for their science.
  5. Provide guidance for future development of the SPIRE scan-map data reduction pipeline.

Test Cases

In total 13 test cases were generated, including data sets obtained in different observational modes and scan speeds, with different map sizes, source brightness, and levels of complexity of the extended emission. They also include observations suffering from the ``cooler burp’‘ effect, and those having strong large-scale gradients in the background radiation. Among the test cases, 8 are simulated and 5 are real observations.

The input data sets for test cases, plus detailed descriptions, can be found here.

Simulations

Comparing to real observations, a simulated test case has the advantage of possessing the ``truth’‘, namely the sky model, based on which the simulation is carried out. The truth map provides an unbiased standard against which test maps made by different map-makers are to be compared. Allowing for the effects of noise in a given map, deviations from the truth can be used as objective measures for the bias introduced by the map-making process.

A detailed description of our simulations can be found here.

Participating Map-Makers

  1. Naive mapper (default of SPIRE SPG until HIPE 8);
  2. Destriper in two flavors: (i) Destriper-P0: Destriper with polynomial-order = 0 (default of SPIRE SPG since HIPE 9), and (ii) Destriper-P1: Destriper with polynomial-order = 1;
  3. Scanamorphos;
  4. SANEPIC (GLS mapmaker);
  5. Unimap (GLS mapmaker);
  6. HiRes (super-resolution map-maker);
  7. SUPREME(super-resolution map-maker).

Map-Making Test Metrics

Results of tests are presented in the framework of four sets of metrics:

(1) Deviation from the truth.
(2) Spatial (2-D) power spectra.
(3) Point source and extended source photometry.
(4) Metrics for super-resolution maps.

The results can be found in the test report (see next section).

The Test Report

A full description of the test campaign and the results (including an Executive Summary) can be found in SPIRE Map-Making Test Report (Version 6; Dec 20, 2013).

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Page last modified on January 08, 2014, at 02:04 PM