SOFIA: Overview

SOFIA Science Data Archive: Overview

The SOFIA Science Data Archive at IRSA is ultimately the repository for all data collected by SOFIA. The archive has data from most instruments (EXES, FIFI-LS, FLITECAM, FORCAST, FPI+, GREAT, HAWC+), Cycles 1 through Cycle 9, with some data from pre-Cycle 1; proprietary data has access restrictions. (More information below.)

Note that there are also SOFIA Science Data Archive video tutorials, available at the IRSA YouTube channel . Look for the playlist collecting all the SOFIA videos in one place.

Contents of page/chapter:
+Background -- A little more about SOFIA
+Terminology
+Instruments & Data Available, and Caveats
+Searching (Quick Start)
+Results Overview
+Visualization Overview -- Image viewing tools
+Downloading Data -- Downloading data in the background
+Logging in
+Getting More Help

Background

SOFIA was an 80/20 partnership of NASA and the German Aerospace Center (DLR), consisting of an extensively modified Boeing 747SP aircraft carrying a 2.7-meter (106 inch) reflecting telescope (with an effective diameter of 2.5 meters or 100 inches). The aircraft was based at NASA's Armstrong Flight Research Center in Palmdale, California. The SOFIA Program Office is at NASA Ames Research Center in Moffett Field, California, which managed SOFIA's science and mission operations in cooperation with the Universities Space Research Association (USRA; Columbia, Maryland.) and the German SOFIA Institute (DSI; University of Stuttgart).

More information about SOFIA and its instrument suite can be found at the SOFIA mission page at IRSA , specifically :

the data page , which includes handbooks and the list of known issues with SOFIA data;
the instruments page , which includes pages for each of the SOFIA instruments.

Terminology

Mission ID is a unique mission identifier. In the SOFIA framework, a mission is the same as a SOFIA flight. (List of all the SOFIA Mission IDs in the SOFIA Science Data Archive , retrieved via TAP .)
Flight Series means a grouping of missions (flights) close in time where SOFIA originates from the same airfield and the same instrument is used.
Plan ID is the identifier for the observing plan which contains all the observations (AORs). Each accepted observing program has a Plan ID; this can be thought of as basically a proposal ID. (List of all the SOFIA Plan IDs in the SOFIA Science Data Archive ,retrieved via TAP .)
AOR is astronomical observation request, an individual SOFIA observation sequence. Each AOR involves many frames, and therefore multiple files.
AOR ID is the AOR identifier. The AOR ID is assigned during the creation of the final version of an AOR to be used in flight. Multiple observations in one or more flights and/or instrument configurations can be associated with a single AOR.
Observation ID is the combination of Mission ID and AOR ID, which together uniquely identifies each SOFIA observation. An observation will contain multiple data files. AOR ID by itself is not sufficient since some AORs are spread across multiple flights.

In practice, during a SOFIA mission (or flight), several Plan IDs (or programs) are executed, and each of these consist of one or more AORs.

The Mission ID, Plan ID, and AOR ID are metadata that can be found in the header of an AOR file.

Data levels

Level 0: raw data in FITS format.
Level 1: raw data in FITS format.
Level 2: data corrected for instrument artifacts (e.g., flat-fielded, dark-subtracted, bad pixels removed).
Level 3: flux calibrated and telluric corrected data (e.g., units of Jy/pix).
Level 4: Any data product generated from the combination of Level 3 files (e.g., a mosaic) is a Level 4 product. For most instruments, Level 4 products could be generated from observations obtained across multiple flights, or even multiple flight series and observing cycles.

Note that not all instruments will have all data levels, and not every flight will have data from every level. The following are the expected data levels, at most, from each instrument:

EXES: 0, 1, 2, 3
FIFI-LS: 1, 2, 3, 4
FLITECAM: 0, 1, 2, 3
FORCAST: 1, 2, 3, 4
FPI+: 1, 2, 3, 4
GREAT: 1, 3, 4
HAWC+: 0, 2, 3, 4

For much more information, see the SOFIA data processing page

Instruments & Data Available, and Caveats

Cycle dates and instruments: Which data are in the SOFIA archive:

Not all instruments, all cycles are in the SOFIA Science Data Archive. The table summarizes which data are in the Archive. (DNE means does not exist, e.g., data do not exist for this instrument in this cycle.) HIPO data are available here .

Cycle	Observation dates	EXES	FIFI-LS	FLITECAM	FORCAST	FPI+	GREAT	HAWC+	HIPO	Schedule/ Flight Plans link
Short Science	12/10 -04/11	DNE	DNE	DNE	No	DNE	Yes	DNE	DNE	...
Basic Science	05/11 - 12/11	DNE	DNE	DNE	No	DNE	Yes	DNE	DNE	...
Cycle 0	07/12 - 11/12	DNE	DNE	DNE	No	DNE	Yes	DNE	here	...
Cycle 1	04/13 - 02/14	DNE	DNE	Yes	Yes	DNE	Yes	DNE	here	here
Cycle 2	02/14 - 02/15	Yes	Yes	Yes	Yes	DNE	Yes	DNE	here	here
Cycle 3	03/15 - 12/15	Yes	Yes	Yes	Yes	Yes	Yes	DNE	here	link
Cycle 4	02/16 - 02/17	Yes	Yes	Yes	Yes	Yes	Yes	Yes	DNE	link
Cycle 5	02/17 - 11/17	Yes	Yes	Yes	Yes	Yes	Yes	Yes	here	link
Cycle 6	05/18 - 03/19	Yes	Yes	DNE	Yes	Yes	Yes	Yes	DNE	link
Cycle 7	04/19 - 03/20	Yes	Yes	DNE	Yes	Yes	Yes	Yes	DNE	link
Cycle 8	08/20 - 06/21	Yes	Yes	DNE	Yes	Yes	Yes	Yes	DNE	link
Cycle 9	07/21 - 09/22	Yes	Yes	DNE	Yes	Yes	Yes	Yes	DNE	link

Data currently in the SOFIA Science Data Archive

Data from most instruments (EXES, FIFI-LS, FLITECAM, FORCAST, FPI+, GREAT, HAWC+), Cycles 1 through Cycle 9, are available in the SOFIA Science Data Archive.

Not in the archive: Some early data through Cycle 0 are not in this archive.

HIPO data are available here
FORCAST commissioning data are available here
Commissioning data for EXES, FIFI-LS, and HAWC+ are available here

There may still be proprietary data, in which case the average user will not have access to all of the data in the archive. See here for more information on gaining access to proprietary data. Eventually, all data will be public.

List of all the SOFIA Mission IDs in the SOFIA Science Data Archive (retrieved via TAP )
List of all the SOFIA Plan IDs in the SOFIA Science Data Archive (retrieved via TAP )

Specific items, caveats, etc. to keep in mind

General information

In an all-sky search, some columns in the result table have missing PLAN ID (i.e., PLAN ID= unknown). These are typically calibration observations.
In an all-sky search, many rows of the result table have the Proposal PI column blank. These are typically calibration observations but may also be data products combining many different observations.
Some observation dates are erroneously set to 1970.
Data that are not public have release dates that are the actual, future release dates. Data that are aleady public may have the most recent processing date, as opposed to the date that the original observations actually went public.
Some AOR ID and Plan ID are erroneously set to obviously incorrect values.
Some positions, especially in the earliest data, have larger uncertainties. Recommend larger search radii to be sure you're catching all the relevant observations.
The Preview tab in the results is only populated for (some) GREAT, FIFI-LS, and HAWC+ Level 4 products, and other instruments (or low level data for any instrument) will have a blank "No Preview Available." This is working as intended.
When NAIF ID appears to conflict with Target Name, believe the NAIF ID. This is most common for some of the calibration AORs.
Some data from the current observing cycle may only be available at Level 1 if the data are still being processed.
If the Observation Type is not OBJECT, do not not necessarily believe the Target or NAIF ID fields; it could be, e.g., flatfields at a completely different position (not the stated target).
On searching for occultation observations: there are two choices. Easier: use the precovery search. Search for the occulter of interest, and look for results with target_moving = 0, which is equivalent to no NAIF_ID. Harder: do an all-sky query and filter the results by the object name of the occulter you're interested in (example: Titan). Results for that object but with no NAIF_ID are likely occultations, since the telescope was pointing at a sidereal target. You can confirm by looking at the proposal abstract in the AOR tab (example: 06_0160).
The GUI filtering menu for Product Type considers blank fields to be "NULL" (for example, FLITECAM raw data), which seems a bit misleading but is working correctly (this is a feature not a bug).

EXES

EXES started operations in 2015, so no data are available before that date.
Level 1 raw files have no Product Type; Level 2 files have Product Type "raw".
The EXES instrument does not have Level 4 data products, so an all-sky query for EXES Level 4 returns no results.
Peculiar values for spectral resolution indicate calibration files.

FIFI-LS

FIFI-LS started operations in 2014, so no data are available before that date.
Peculiar values for spectral resolution are shown here as propagated from the FITS headers.
Level 4 wxy_resampled, HDU 10, display shows pixels in units of Jy even though it's a coverage map.

FLITECAM

FLITECAM was retired in 2018, so no data exist after that date for this instrument.
The blank spectral resolution for FLT_A1_LM (energy bounds 4.4-5.53 microns) is working as intended; the Observer's Handbook doesn't list R for that combination of grism and order sorting filter.
The FLITECAM instrument does not have Level 4 data products, so an all-sky query for FLITECAM Level 4 returns no results.
OC1E FLITECAM data is only Level 1, so there is no Level 2/3.
Some data products may be included in the download that according to the Data Handbook should not have been saved or archived.

FORCAST

The FORCAST instrument only rarely has Level 4 data products, so an all-sky query for FORCAST Level 4 returns relatively few results.
The cross-dispersed modes, X-, were not used in Cycle 4 and Cycle 5, so an all-sky query for FORCAST, GRISM, FOR_XG063 or FOR_XG111, returns 0 results.
The FORCAST definition of SW and LW cameras is fluid so a few short wavelengths (such as 6.4 micron and 11.2 micron) fall under the LW category. This should not surprise the user. A complete definition of SW and LW cameras is provided in the Observer's Handbook, which can be found on the Proposal Documents page .
Users should be aware that in the FORCAST query menu, the second number that appears on the Spectral Element menu is the filter width (in microns) of a given filter. This is not the same as the spectral resolution, which is the quantity provided in the FORCAST result tab under "Details". Most spectra are resolution (R)~100; cross-dispersed spectra (XG*) are R~1000. Medium and narrow-band imaging filters can also have a resolution (R~45-70).
FORCAST footprints in the coverage tab may be larger than expected. NAXIS* and CDELT* are the same for different levels, yet Level 1 is shown with a much smaller footprint than Levels 2-3. The valid data really is a 256x256 square, but the Level 2 coadd has an actual fits header with NAXIS*=656, with the valid data embedded within a square of NaNs. The coverage software sees the 656 pixel dimensions in the actual FITS headers and draws the larger square.
FORCAST FOR_F086 energy_bounds and spectral resolution may not be populated.

FPI+

FPI+ started operations in 2015, so data is only available after that date.
The FPI+ Instrument Team has not generated an instrument handbook, so this is not currently available.

GREAT

The GREAT instrument does not have Level 2 data products, so an all-sky search for GREAT Level 2 returns 0 results.
Not all the GREAT data are in FITS format. All the Level 1 data are FITS files, while Level 3 data are tarfiles consisting of CLASS files, and Level 4 can be either CLASS or FITS. (Level 2 data do not exist for this instrument.)
GREAT Level 4: velocities derived by Firefly are wrong.
GREAT previews may not exist for all data.
For the GREAT instrument, a frequency channel is defined as a delta function, not as a Gaussian with a FWHM. This has to be kept in mind when performing a query by frequency. This is not the case for the other instruments.
Some early GREAT observations have low spectral resolution (~1e3 instead of the usual ~1e7) from a rarely-used continuum mode.
Some GREAT Line values seem unusual, like an observation of Jupiter with Line="L2_saturn", but those refer to continuum settings originally used on one calibrator but that may sometimes be used on others.
GREAT files with INSTMODE=CAL have incorrect coordinates, target name, and NAIF ID. Unfortunately the INSTMODE keyword isn't visible to users without downloading the files
The GREAT Instrument Team has not generated an instrument handbook, so this is not currently available.

HAWC+

HAWC+ started operations in 2016, so HAWC+ data is only available after that date.
The raw data from HAWC+ correspond to Level 0 rather than Level 1. (Level 1 is raw for all the other instruments.)
A few early HAWC+ observations used both band A and B in the same Observation, which results in the band B energy_bounds not being computed correctly since the ingest code sees a band A Observation and doesn't expect or allow for spectral elements to change within an Observation.

Searching (Quick Start)

Several search options are provided, which are documented in more detail in the Searching section.

Searching by position is the most popular search, and you can also search in "batch mode" by uploading a table, from your local disk or the IRSA Workspace (which is a bit of disk space for you at IRSA).

You can also search for Solar System objects by NAIF ID.

You can add additional constraints to, e.g., show only observations from one program or one flight or one instrument. Go to the Searching section for much more detailed information.

Results Overview

The search results appear in two "panes" (like "window panes"). You can grab and drag the division between the two panes to change their relative sizes.

The left pane of the search results contains lists of observations that met your criteria. The right pane of the search results contains more details of the observations. The right pane changes depending on what row you have selected (clicked on) in the left pane. (And the left pane can change depending on what you have selected in the coverage image in the right pane.)

Proprietary data (to which you do not have access in general) are red rows; public data are white rows.

The basic table manipulation tools are documented in the Tables section.

For more information, see the Results section.

Visualization Overview

Any images meeting your search criteria are shown as the results of the search, in the instrument tabs. The small circle overlaid by default is the search position you submitted.

Move your mouse over any image that is returned by your search. Details about the image and, specifically, the pixel beneath your mouse cursor, appear along the bottom of the window with a variety of useful items (see screenshot below). Some information is updated in real time (such as coordinates); some information (such as flux densities) is updated when you stop moving your mouse for a second or two. The image can be interactively investigated in this fashion.

There is a toolbar across the top of the window pane from which you can interact with the displayed FITS image files -- you can control the stretch, add a coordinate grid, etc. Clicking on the icon that looks like this: enlarges the images to take up more space in the browser, and you can further zoom to make a single image take as much space in the browser as possible. You can scroll through all of the images in this maximally "zoomed-in" view. You can also add or remove overlays (such as coordinates or distances) to your images. See the Visualization section for more on visualization.

Downloading Data Overview

You can download to your disk the observations you have selected. Check the box at the start of each row (or the box at the top of the column of boxes to select all) and click "Prepare download." See the section on Downloads or the section on the Background Monitor for more information.

Logging in (Overview)

The SOFIA Science Data Archive can remember you when you return. See the user registration section for more information.

The SOFIA Science Data Archive contains proprietary data; if your data are proprietary, you need to register and log in jin order to get access to your SOFIA data.

Getting More Help

The "Help" blue tab leads you into this online help. There are also context-sensitive help markers throughout the tools (

). You can also download a PDF version of this manual; look at the top of the help window. (The PDF may be easier to search than the web pages; use your PDF reader's search function.)

You can submit questions to the IRSA Help Desk .

The IRSA YouTube channel has lots of short videos about IRSA tools, including specifically SOFIA.

A set of frequently asked questions (FAQs) is here.

Found a bug? The known bugs and issues in this version of the SOFIA Science Data Archive are listed here . If you think you have found a bug, before reporting it, please check this list, and read this online help. It may be a "feature" we already know about. If you have found a new, real bug then please do contact us via the IRSA Help Desk . Please include your operating system version and your browser software and version. If you can, please also include any specific error message you may have gotten. (NB: In our testing, copying shortcuts worked on Windows and Linux; the command-C did not work on Macs, but selecting and clicking the right mouse button did.)