OYSTER was created when three collections of scripts written first in
PV-WAVE Command Language (PV-WAVE is a trademark of Rogue Wave Software)
and then also in the Interactive Data Language (IDL is a trademark of
Exelis Visual Information Solutions) were merged into one for the purpose
of providing a comprehensive data analysis package for the Navy Prototype
Optical Interferometer at Lowell (NPOI). The three original collections
are CHAMELEON, which reduces a single night of data, AMOEBA, which fits
models to the calibrated visibility data of several nights, and STARBASE,
which implements a stellar data base and provides catalog access.
Also introduced are new collections of scripts, namely COBRA, which
provides functions for the interactive analysis of raw interferometry
data and PEARL, which images interferometric data. STARWHEEL is still
in a design phase for an interferometric observation planner.
The name OYSTER was derived from OISDR (Optical Interferometer Script Data Reduction).
The Navy Prototype Optical Interferometer developers believe in real world
naming of software.
OYSTER is a 40,000+ lines of code project to provide a
comprehensive system for displaying, editing, averaging,
calibrating, and modeling interferometry data. It has been developed
by Dr. Christian Hummel over several years at the US Naval Observatory
and the European Southern Observatory. PV-WAVE CL and IDL were chosen
as the programming environment because they provide interactive
data manipulation and extensive plotting and visualization tools. Coding
and debugging are very fast in this environment.
OYSTER is an endeavor to integrate all tasks related to planning
and analysing interferometric observations in one package. It also
tries to maximize ease of use by providing both command line procedures
and widget routines. A 100-page manual is provided. Users can also
find instructions on how to build their own library of procedures which
take the place of and modify the implemented procedures by compilation
Available features of OYSTER include:
- HDS data base access: A full set of functions to access NPOI data files
written in the Hierarchical Data System format (developed by Starlink).
Individual objects can be accessed directly.
- Plotting and editing: General plotting widgets, with interactive
display options and editing routines. Flagtables are implemented for
- Astrometry: Multi-color dispersion corrections, metrology calibration,
astrometric functions including the Naval Observatory Vector Astrometry
Subroutines, epoch conversions, and polar motion data. Solution for
baseline and star coordinates. Global astrometry using sparse matrix technology.
- Calibration: General multi-dimensional visibility amplitude and phase
calibration capability for several types of dependencies.
- Global modeling: Use of a hierarchical stellar systems format which
enables fitting physical parameters directly to any combination
of data from interferometry, spectroscopy, photometry, and astrometry.
- Imaging: provides tools for imaging composite spectrum binaries.
- Stellar spectra and limb darkening: atmospheric models which are used
in bandwidth smearing computations and modeling. Display of stellar
spectra and line identifications.
- Stellar data base: procedures for star catalog access. Storage of data
in a table, and procedures for estimation of physical parameters
of stars, like diameters, masses, orbital elements.
- Planning of observations: A set of procedures for computing
visibility and simulating data for scheduling. The stellar data base
serves to aid in the selection of calibrator stars.
- Archive of data: List past observation dates, stars, number of scans,
and other information.
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