Science Archive

The SOFIA Science Center provides raw and calibrated data for all instruments via the Data Cycle System (DCS) Science Archive. Archival data is publicly available for data that has passed its exclusive-use period and for data from SOFIA's Director's Discretionary Time programs, which have no exclusive-use period. More information about approved DDT programs and currently available DDT data can be found here.

A DCS account is required to search the DCS Science Archive and download data. Register for a DCS account here

Information on transition to IRSA archive:

SOFIA is beginning to transition to using the Infrared Science Archive (IRSA) hosted by the Infrared Processing & Analysis Center (IPAC) as its primary data archive. The first release of the SOFIA Archive at IRSA includes FIFI-LS, FORCAST, and GREAT data from Cycle 4 and Cycle 5, and is currently accessible online. By the end of 2019, the second archive release will expand the database to include SOFIA data from all instruments and all cycles.

For tips on SOFIA specific archive searches and taking advantage of IRSA visualization features, check out the video tutorials here


Gathering and Navigating SOFIA Data

Whether you have completed your own SOFIA observations or want to use publicly available datasets in the archive, below are a few tips to help you get started with exploring SOFIA data.

Jump to Section:

Accessing the Archive
Quering the Archive
Selecting Relevant Data Products
Exploring Data Package Contents

Accessing the Archive

All raw and processed SOFIA data are stored in the SOFIA Science Archive. Data which are still in its exclusive-use period are accessible only by the designated Guest Observers on the project, and delegated users; all other data are publicly accessible. The science archive can be searched by any registered user. If you are a new user, you need to register for a DCS account.

Note: SOFIA is beginning to transition to using the Infrared Science Archive (IRSA) hosted by the Infrared Processing & Analysis Center (IPAC) as its primary data archive. The first release of the SOFIA Archive at IRSA includes FIFI-LS, FORCAST, and GREAT data from Cycle 4 and Cycle 5, and is currently accessible online. By the end of 2019, the second archive release will expand the database to include SOFIA data from all instruments and all cycles. 

For tips on SOFIA specific archive searches and taking advantage of IRSA visualization features, check out the video tutorials here

Querying the Archive

After entering your login credentials in the SOFIA Science Archive, you can launch a query. Select Advanced Search to access all of the search features. Some common queries include the following:

  • proposal ID (Plan ID field)
  • PI name. Note that those fields are accessible by clicking on the 'advanced search' button. These fields are often used to find one's own data. 
  • target. A target name can be entered and matched to known coordinates in the SIMBAD or NED catalogues through the corresponding buttons. Alternatively, coordinates can also be entered directly (equatorial or galactic). It is recommended to enter a relatively large spatial search radius (for example, 600 arcseconds) to avoid excluding relevant observations.
  • instrument (and corresponding instrument configuration drop-down menus)
  • wavelength range
  • observation dates

Selecting Relevant Data Products

The Processing State drop-down menu allows one to query only products corresponding to a given processing state (level). Generally speaking, Level 0 and Level 1 correspond to raw data, and Level 2 to data corrected for instrument artifacts. Level 3 (flux calibrated data) and Level 4 (higher level processing, such as combined observations, large maps) are usually the data processing levels most useful for scientific analysis. Starting a search with Processing State = Level 3  is the recommended way to proceed, as Level 4 products are not produced for all observations. See the Data Processing webpage for information on processing levels.

The Product Type field can also be used for a more specific product search. For a detailed description of the products types available under each processing state for a given instrument, it is recommended to download the corresponding data handbook from the Documentation for Data Products webpage, which contains a detailed description of the pipeline calibration process and the pipeline products.

Click the Submit button to submit the query.

Downloading Data Products

Running a query results in a table that lists individual products and/or tar files grouping several products. If you searched for Level 3 products, each row corresponds to a unique combination of AOR (Astronomical Observing Request, corresponding to a spatial and spectral setup linked to a given proposal), Observation ID (time unit of data processed together, which can be as short as a few seconds or as long as several flight legs), spectral element and product type. If you searched for Level 4 products, table rows can also correspond to combinations of AORs and Observation IDs, possibly across several flights.

Select the the product(s) you would like to download using the check boxes on the left of the table, then click on Get Selected Data in Current Page at the top of the table. This produces a page where you can now see the full name of the selected products in the Original File column. Then click on Request Data Bundle.

The data bundle will be delivered to you as a download link to a zip file from "The SOFIA Data Cycle System" via the email associated with your DCS account. The time it takes to receive this email varies from a few minutes for a small download (< 1 GB) and several hours for large downloads. For downloads between 2-30 GB, you will receive an email with multiple links for each 2GB section of the data set. If you do not get that email, try the action again and contact the Help-Desk.

Download the zip file(s) by selecting the download link in the email, unzip the files, and combine them following the instructions in the email (if necessary).

Exploring Data Package Contents

The data package is organized in a series of embedded directories, described here from upper level to lower level. This structure may vary slightly across instruments and observing cycles, and not all directory levels may be present.

  • If both Level 3 and Level 4 data were downloaded, they will be stored in different upper level directories, labeled missions and level4 respectively
  • Under these upper level directories one may find one directory per flight, named after the corresponding mission ID (for example 2018-07-05_HA_F481), as well as directories for products produced from different flights processed together.
  • Within those, one can find subdirectories for each pipeline processing run, labeled pNNNN.
  • Each pipeline processing directory is possibly further divided in several directories for each spectral element/AOR combination.
  • The Level 3 and Level 4 products can then be found. Those are usually are in the .fits format. (For GREAT data, data in .great and .lmv format can also be found, as well as an additional directory with informative files)

Filenames can give you information on the nature and content of the file even without looking at its header. Typically, a filename follows the template Flight_IS_MOD_AOR-ID_SPECTEL_Type_FN1-FN2.fits, where Flight is the SOFIA flight number, IS is the instrument identifier, SPE specifies the instrument mode, AOR-ID is the 8 digit AOR identifier for the observation, SPECTEL is the keywords specifying the spectral configuration, Type are three letters identifying the product type, FN1 is the file number corresponding to the first input file, and FN2 is the file number corresponding to the last input file.

Collecting Information on Data Quality
All processed data have been through a quality analysis examination to determine whether they are usable. Comments on the data quality and suggestions on the best way to analyze the data may have been recorded. Those comments can be essential to understanding the data. Such comments can be found in the headers of Level 3 and Level 4 products, at the bottom of the HISTORY key.

  • Note that for GREAT data, the comments can be found in the data reduction pdf included in the dowloaded data package (note that not all GREAT Level 4 packages contain the data reduction pdf, and it is sometimes necessary to download the corresponding Level 3 packages to obtain that file).
  • Known data issues associated to each flight (listed by mission ID) are also collected in the following document, which is regularly updated: https://www.sofia.usra.edu/sites/default/files/USpot_DCS_DPS/Documents/D....

Gather Information on Observations:

  • Information on observation specifics can be found under the header keys in the fits products, such as EXPTIME (Total on-source integration time), WVZ_END and WVZ_STA (water vapor).
  • For GREAT data, comments on observations can be found in the observing log pdf included in the downloaded data package (note that not all GREAT Level 4 packages contain the data reduction pdf, and it is sometimes necessary to download the corresponding Level 3 packages to obtain that file)
  • If you are the guest observer of the proposal from which the observations were performed, we recommend examining the flight reports which were sent to you by the instrument scientists after each of your observations was acquired. Those may contain useful information on observing conditions. 

You have now collected all the available data and information to start data analysis. If you are not familiar with SOFIA data, you may find it useful to look at our data recipes, which were written to show how to make simple plots and carry out basic data analysis tasks.

Contact the Help-Desk for any question related to your data. The staff at the SOFIA Science Center is there to support you in your exploration of your data.

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