K2 Online Ancillary Files
(updated June 25, 2018)

As was done for Kepler, several types of online ancillary data files are made available to users. The currently available ones are described below with links to the corresponding subdirectories of the K2 directory. Note that the Long and Short Cadence Collateral (KLL & KLS) files, Artifact Removal Pixel (KAP) files, and Background Pixel files (KBG) are stored elsewhere but can be retrieved using the FFI & Ancillary Data search form. These file types are documented in the Kepler Archive Manual and the differences for K2 products are noted in the K2 Data Release Notes.

• Cotrending Basis Vectors (CBV) Files
  The CBVs may be used to mitigate instrumental signatures in K2 light curves when the PDC light curves are inadequate. CBVs are available for most campaigns starting with Data Release 5 (see the table at archive.stsci.edu/k2/cbv.html).
  
  
• Full Frame Image (FFI)
  Full frame images of the K2 fields are typically taken twice during each campaign to confirm the field of view, assess photometer health, and facilitate calibration. The FFI files contain both raw (*orig.fits) and calibrated (*cal.fits) images as well as uncertainties (*uncert.fits). They can be downloaded using the browser at the above link, anonymous ftp at /pub/k2/ffi, or via the FFI & Ancillary Data search form.

  There are also five experimental driftscanned raw FFIs here from Campaign 17.
  See the README file for more information.

  To display individual channels from any of the FFI images, and overlay various catalogs, see the FFI_Display page.
  
  

• Fine Guidance Sensor Data (FGS) The FGS data collected throughout the K2 mission are being made available to the user community for scientific analysis as flux and centroid time series, along with a limited number of FGS full frame images which may be useful for constructing a World Coordinate System (WCS) or otherwise putting the time series data in context.
  
  
• SPICE Kernels for K2
  The latest SPICE kernels (i.e., the bsp and tsc binary files) can be used to calculate the Kepler spacecraft ephemeris. These files are available via anonymous ftp at /pub/k2/spice, or via the browser at the above link. See the Navigation and Ancillary Information Facility (NAIF) web site for information on using SPICE Kernels.
  
  
• Thruster Firings
  Starting with Data Release 5, the QUALITY flags included in the light curve and target pixel FITS files indicate cadences at which thrusters fired, or may have fired. Now that all Campaigns have been reprocessed, all Campaigns (except 9 and 10a) have these flags set, and the stand-alone thruster firing table has been removed. See Table 2-3 in the Kepler Archive manual for the definitions of these new bit flags. For Campaigns "91", "92", and "101", the thruster times are available in the Data Release Notes for those Campaigns, which can be found in the last Campaign 9 DRN and the last Campaign 10 DRN, respectively.
  
  
• Raw Cadence Data
  Raw cadence data are generally released immediately after download from the Kepler spacecraft to facilitate time-critical investigations which would be unduly delayed by waiting for the pipeline-processed data that contain both calibrated and uncalibrated pixels in the standard TPF format.

  These raw cadence data consist of multiple components, including target pixels, collateral pixels, and pixel mapping reference files. For more information on format and usage, see the document KADN-26315.pdf, and consider using Kadenza to convert these raw data to a more user-friendly file format. We currently have raw cadence data for campaigns 0 through 17 and pixel mapping reference files for campaigns 0 through 19 online.
  
  

• Two-wheel Concept Engineering Test Data
  The data from a 9-day engineering test conducted before Campaign 0 have been made available as uncalibrated TPFs. These files can be downloaded individually or as .tgz files (there are 17 targets in the 4 GB short cadence compressed file and 2,079 targets in the 16 GB long cadence compressed file). To download from the browser use the link above, or ftp to archive.stsci.edu and cd to /pub/k2/eng. The individual files can be found in subdirectories labelled "short_cadence" and "long_cadence". The .csv files provide a brief description of why these targets were observed and map their engineering IDs to their locations and estimated Kepler magnitudes.
  
  
• Download Scripts
  These WGET scripts allow light curve or target pixel file data to be downloaded for a particular program ID. These scripts should be downloaded to the users' computer and run from its command line. They require WGET to be installed on the users' computer.
  
  
• Previews
  Previews are various size png plot files showing K2 light curves.