Table of Contents
The TESS mission has several data products ranging from the TESS input catalog to a catalog of planet candidates. Here we give an overview of what information is in each data product.
Photometric Data Products
TESS obtains time-series photometry at two different cadences with a baseline ranging from ~27 days to a full year, depending on sector overlap. An overview of the primary pixel-level science products are shown above. The entirety of the CCDs are downloaded every 30-minutes, these are known as the Full Frame Images (FFIs). Certain groups of pixels are also downloaded at a 2-minute cadence in order to obtain a faster cadence for a subset of targets, these are known as Target Pixel (TP) files. The pixels around a selected star are stored as arrays in these target-pixel files, one image per time stamp. Aperture photometry is performed on each image creating an array of fluxes; these are known as Light Curve (LC) files. See the Science Product Handbook for more detailed information on file formats and content.
- Full Frame Images (FFI) (uncalibrated: _ffir.fits, calibrated: _ffic.fits): These files contain the long cadence time series of the entire field of view, both an uncalibrated and calibrated version are available.
- Target Pixel (TP) Files (_tp.fits): These files contain a time series of the raw and calibrated pixels downloaded at the 2-minute cadence.
- Light Curve (LC) Files (_lc.fits): These files contain the flux time series derived from the calibrated short-cadence pixels. These files contain several time series including the simple aperture photometry, a detrended light curve, position vectors, and quality flags. The aperture photometry flux series is known as the SAP_FLUX, while the flux series that has the common instrumental systematics removed using the CBV files is known as the PDCSAP_FLUX.
Cotrending Basis Vectors (CBV) (_cbv.fits): The cotending basis vectors represent the set of systematic trends present in the ensemble light curve data for each CCD and can be used to remove common instrumental systematics from the data. These vectors are created by the pipeline to produce the detrended flux time series (PDCSAP_FLUX) in the light curve files. The CBVs can be fit to individual aperture photometry light curves (known as SAP_FLUX) on the same channel in order to fine tune the detrending.
Table: Cadence Quality Flags
The TESS pipeline populates a series of quality flags to indicate when a cadence may have been taken during an anomalous event. These flags are available in the light curve files, the target pixel files, and a subset are available for the FFIs. Those in the FFIs are created by taking a logical AND across the short cadences. The following table describes the meaning of each flag.
n Binary Digit # | Value = 2(n-1) | In FFI? | TESS Quality Flag Description |
|---|---|---|---|
| 1 | 1 | y | Attitude Tweak |
| 2 | 2 | n | Safe Mode |
| 3 | 4 | y | Spacecraft is in Coarse Point |
| 4 | 8 | y | Spacecraft is in Earth Point |
| 5 | 16 | y | Argabrightening Event |
| 6 | 32 | y | Reaction Wheel Desaturation Event |
| 7 | 64 | n | Cosmic Ray in Optimal Aperture Pixel |
| 8 | 128 | y | Manual Exclude due to an anomaly. |
| 9 | 256 | n | Discontinuity corrected between this cadence and the next one. |
| 10 | 512 | n | Impulsive outlier removed before cotrending |
| 11 | 1024 | y | Cosmic ray detected on collateral pixel row or column |
| 12 | 2048 | y | Stray light from Earth to Moon in Camera FOV |
Table: Aperture Mask Image Flags
The light curve files and target pixel files contain an image in the APERTURE FITS extension that describes how each pixel was used in the processing. The integer values of this image are the bit-wise OR of the bits described in the following table.
| n Binary Digit # | Value = 2(n-1) | Description |
|---|---|---|
| 1 | 1 | Pixel was collected by the spacecraft. |
| 2 | 2 | Pixel was in the optimal photometric aperture to calculate SAP_FLUX. |
| 3 | 4 | Pixel was used in background calculation. |
| 4 | 8 | Pixel was used to calculate the flux weighted centroid. |
| 5 | 16 | Pixel was used to calculate the PRF centroid. |
| 6 | 32 | Pixel is on CCD output A |
| 7 | 64 | Pixel is on CCD output B |
| 8 | 128 | Pixel is on CCD output C |
| 9 | 256 | Pixel is on CCD output D |
Target Catalogs
TESS provides several catalogs of target stars in order to choose which stars will be observed at the 2-minute cadence.
- TESS Input Catalog (TIC): Catalog of luminous sources in the sky created by the TESS Stellar Properties Working Group, used to select targets to observe at short cadence. It is also used to estimate flux contributions of stars within pixels. The TIC is available through the MAST Portal, CasJobs, via the API/astroquery, and as a direct download split into a series of .csv files.
- Catalog Target Lists (?CTL): Several lists of TIC stars that idicate the priorities for short-cadence observations from different science perspectives. The same TIC ID may appear in more than one list. See the figure above for the names of the various CTLs. Some CTLs, such as the xCTL, are available for download and searching at MAST.
- Merged Target List (MTL): This list represents the final set of targets that are observed at the 2-minute cadence. It is created by selecting targets in the various CTLs plus specific engineering targets. Each target in the MTL should have a target pixel file and light curve file created from the mission pipeline.
Planet Search Products
The flux time series for each star observed in short cadence are then further detrended and searched for transits. The repeating signals that are identified in this way are known as Threshold Crossing Events (TCE). The following products are produced by the TESS Science Processing Pipeline for each target star that produces a TCE.
- DV Time Series File (.dvt.fits): These files contain the sector-stitched, detrended and whitened light curves searched by the TESS Pipeline. All TCEs found on a star in one search are contained in the same file.
- DV Report (.dvr.pdf): These pdf files contain plots and statistics for every TCE assigned to a given TIC target. For example, the reports contain plots of folded light curves and in- and out-of transit difference images.
- DV One-Page Summary (.dvs.pdf): This one page summary contains a quick overview of each individual TCE and much of the most important information about the TCE to determine if the signal is likely caused by a transit or shows evidence of being caused by an eclipsing binary or instrumental noise. Each TCE gets its own file, so if multiple TCEs are found on the same TIC target, there will be multiple _dvs.pdf files for that target. These files are very similar to those produced for Kepler and a description of some of the metrics on this page can be found here.
Exoplanet Result Catalogs
TESS produces several catalogs of possibly transit-like, periodic signals found in the TESS data. As signals are vetted they are can be included in the next catalog down. The catalog of signals with the least amount of vetting are the Threshold Crossing Events (TCEs) which are produced by the SPOC Pipeline. Other groups may also search the short cadence light curves, or the longer cadence FFIs for signals that may be consistent with transiting exoplanets. Since these signals have little-to-no vetting, the reliability can be quite low. Signals found in the data are then turned into TESS Objects of Interest (TOI) once the signal is vetted and determined to be sufficiently consistent with a transit or eclipse. The TOI list contains both planet candidates and false positives, but these are the signals that are worthy of follow-up observations. Once follow-up measurements, or additional analysis, reveal the mass of the transiting object, or remove all doubt that the signal could be caused by an eclipsing binary, the planet is considered confirmed.
- Threshold Crossing Events (TCE): Table of TCE signals and various metrics that measure different aspects of that signal. For each TCE, the project provides a highly detrended light curve file and a report showing relevant plots to evaluate whether the signal is a planet. The project also provides an xml file for each star that contain all the information related to the TCEs found in that star's light curve. These signals are not vetted and include various types of false positives and instrumental false alarms. Each TCE is identified by a TIC ID, planet number and search ID.
- TESS Objects of Interest (TOI): Table containing the list of signals that are consistent being a transiting planet. This catalog provides a disposition of either planet candidate or false positive which can change as more information is gathered about a target from follow-up and additional analysis of the data.
- Confirmed Planets: Transiting planets found in the TESS data for which follow-up data provide a mass of the planet. See the exoFOP-TESS page for more information about what follow-up data are available.
Engineering and Model Files
These files include the Pixel Response Function, the Flat Fields, the Black Model and Engineering Mnemonics. See the full listing of the data products.