In this PACS Products Explained (PPE), the products that PACS spectroscopy and photometry provide to the astronomer via the Herschel Science Archive (HSA) are explained. From the HSA one can request an entire observation, chose from a single completed pipeline Level, or ask for only the Standalone (Browse) Products. In this document we will describe what is contained in these choices, and highlight which products are the most useful for the different types of observation and science.
In Chapter 2 we explain what is found in the entire observation (the ObservationContext). This context contains the entirety of an observation, from the raw to the reduced astronomical data as well as instrument and satellite data, all of which was/will be necessary to process/reprocess the science data. In this chapter the contents of an ObservationContext are explained: what is found in each Level and how they are organised. In particular for spectroscopy, the differences between the various types of cubes provided for any observation are explained. The layout of an observation in HIPE and on disc is explained, so you know which product to get be it via HIPE or as a FITS file directly from an HSA download.
In Chapter 3 we give more detail on the datasets in the final level (2/2.5/3) pipeline products.
In Chapter 4 the Meta data and FITS keywords of the Level 2/2.5/3 maps, cubes, and tables (i.e. for products of interest to archive users) are listed. This is essentially a reference chapter.
In Chapter 5 we highlight the Standalone browse products, which can be downloaded directly from the HSA, and are also found in any ObservationContext produced by SPG 13 and higher. These products are either exactly the same as (photometry), or different versions of (spectroscopy), some of the final-level pipeline products. The "SBPs" are the products that are recommended for general use, for example to have a first look at what is in the data. Whether these products are the ideal ones to use for every possible type of science depends, however, on the science case.
In Chapter 6 we give recommendations about which products to take from a PACS observations, depending on the science case and also the observing mode. We also give the prerequisites for use of these products for your science.
This document accompanies HIPE Track 15.
If you use the interactive pipeline scripts of this version of HIPE to re-process your data, you will be creating Track 15 products, and you should be using using the final calibration tree that was released. The range of products you create will depend on the particular interactive pipeline script you use and what type of observation you have, and their names will naturally depend on whatever naming convention you decide to use.
Observations downloaded from the HSA are created by a bulk processing using the specific version of the pipeline scripts called the "SPG" (standard product generator) scripts, and using the calibration tree available at the time of the SPG processing. If your HSA-obtained data are not recent (SPG v13 or earlier), it is probable that there will be some differences between the products in the observation you have and the products explained here: it is always advised to work with the latest SPG version of data from the HSA so you not only have all the products we offer, but you also have the products that were also processed with the latest calibration tree.
The final processing of PACS data is SPG 14.2.x: for all observation a processing was done in 14.2.0 and for some observations a re-processing was done in 14.2.1 and 14.2.2: see the "What's New in HIPE 14" pages on the HSC web-site for details. Since the final SPG was run at the end of 2016, by the time you read this every successful observation in the archive will have had its final processing, and the precise SPG number will be irrelevant.
A note about fonts used in this document. Italics are used to indicate a Product class: so ObservationContext is used to indicate a product of class "ObservationContext". Different product classes have different capabilities, hold information of different types and in different ways, and can be accessed by different task and GUIs. For the user, the main reason to know the class of a product is to know what tasks and tools will work on them, and to know how to manipulate them on the command line.
The "SPG" version of an ObservationContext can be determined either by looking at the columnar listing of observations in the HSA GUI before you download the data, or, once you have the ObservationContext in HIPE, by opening the Observation Viewer on it (double-click on it in the Variables panel, it is probably called "obs") and looking at the "Summary". Alternatively, the FITS keyword CREATOR, which will be in any science pipeline product you look at, contains this information.