KI Data overview and access
Contents
- Data flow
- Data access
- Interferometer modes
- Formats for Level 1 and Level 2 files and plots
- Qualilty assessment
- Data rights
Data flow
Raw data from the interferometer is stored in files which are archived by the NExScI. These files contain both science and engineering data and are called Level 0 files, as they are unprocessed data. The volume of raw data varies with the observing mode and instrument parameters but ranges from 10 to 40 Gbyte per night. Access to Level 0 data is available only on request (contact your support scientist or the help desk page).
The V2 Level 0 data are processed into fringe amplitudes and other necessary information by a program called Kvis (see the data reduction manual for details). This processing is done automatically at the end of each observing night. At the output of this reduction we obtain Level 1 data, i.e. fringe data that have been corrected for detector biases and averaged, but not yet corrected for the system visibility. The Level 1 data are contained in a group of files, described in detail in the links below. The primary data files are called .sum and .spec files which contain the wideband (or white light) and narrow band data respectively. The prefix for Level 1 files is the UT observation date in the form yyyyddd. In addition to the fringe amplitudes, these files contain other information (delay line positions, time, etc.) needed to calibrate the data for the system visibility (by the programs wbCalib and nbCalib as described below). In addition, there are files which contain other instrument information such as the baseline (.baseline), as well as ancillary data (.anc) from various sub-systems (e.g. angle tracker and adaptive optics systems). The nulling data are also processed through a pipeline to produce Level 1 files, see below.
Once the KI user has obtained his/her Level 1 data for science targets and corresponding calibrators, the programs wbCalib and nbCalib (for V2 data) take these files as input in order to produce fully calibrated Level 2 data. At this time, KI users must calibrate their own data, a task that is greatly simplified if making use of our calibration packages, which may be obtained from our software download page.
Data access
The Level 1 data are available through a web interface which accesses all the desired Level 1 data from a database. The database allows selection of data across many nights and using a variety of selection criteria. For instance, all data with a given project ID, or a for a given target, or for a range of dates, can be retrieved in one query. The interface allows exporting your L1 data in ASCII or FITS formats.
All PIs of a KI observing program have an account created when their data are obtained, please contact your contact scientist with if you are a KI PI and do not know how to access your web data account.
Non-PI users will be allowed to obtain KI data as it becomes public by obtaining a public account to our web access tool.
Interferometer modes
The KI operates in a variety of modes. The KI data is tagged so that data for a given mode can be identified and accessed. The modes currently under operation, and their corresponding mode tags are as follows:
| KI Mode | Mode Name |
| Visibility amplitude in the near-infrared | NIRV2 |
| Nulling (mid-infrared) | Nulling |
Formats for L1 and L2 files
The KI Level 1 and Level 2 data are available in both FITS and ASCII formats. The following links detail the file format in each case:
- Detailed description of V2 L1 and L2 ASCII files.
- Detailed description of V2 L1 and real-time plots
- Detailed description of Nulling L1 and L2 ASCII files.
- Level 1 FITS description.
- Level 2 FITS description (IAU OI-FITS standard).
Quality Assessment
As part of the Level 1 file set, we include information which characterizes the data quality at different levels. For details, please consult the QA help page.
Data rights
The default data proprietary period is 1 year unless an extension is requested of and granted by the NExScI Executive Director. Shared-risk and Key Science programs may have different proprietary periods.
In general, requests for extensions should fall into the following categories:
- Time varying objects with periods of order 12 months or longer in which full period coverage is necessary for the science and more data are expected in the near future.
- Programs in which some data were collected, but the program was not completed in the allocated time due to significant instrument problems.
last updated June 11, 2008