Next: 1 Glossary of Terms
Up: No Title
Previous: 9 Acceptance Suite
Overview
The term ``calibrations'' encompasses a large range of issues and
procedures, and the current document is not
exhaustive. We focus on photometric and
astrometric calibration of direct images through the standard
DEIMOS filter set (BVRI) and flux and wavelength calibration of
multislit spectra, including longslit spectra of single objects as a
special case. These categories comprise the great bulk of
DEIMOS data. We further assume that the instrument consists of
Side A only, although the coordinate systems for Side B have
also been defined.
Two data calibration modes are considered:
-
Pipeline Mode:
- This is analogous to
the current mode for reducing Hubble Space Telesccope data, in which
a standard suite of reduction programs removes the instrumental
signature using a stored library of calibration data. The necessary
software would be supplied by the DEIMOS project and would
run both at Keck and at the observer's home institution (provided
the appropriate hardware and operating systems are available). The
ultimate aim is that pipeline data reduction will occur on-line as the
data are taken, with observers returning home with data
from which the instrumental signature has been removed. A further
longterm aim is to minimize taking calibration data during
observing and to use instead the stored library of calibration data
to the fullest extent.
Pipeline
Mode at this point is only a goal. Its implementation is not supported by the
current DEIMOS software budget, and it further presupposes stability of
the (Keck II Telescope + DEIMOS) hardware system, which is currently unproven. Nevertheless,
we are hopeful of implementing Pipeline Mode eventually and are designing
the DEIMOS database to be able to accomodate it.
- Baseline Mode:
- Baseline mode is the traditional mode
of data reduction at ground-based observatories, in
which each observer is responsible for gathering the necessary calibration
data and reducing the data. We recommend recipes for doing this
with DEIMOS and outline a partial
long-term calibration data base that will be useful for certain aspects
of Baseline Mode calibrations ??. Software and database entires needed
to implement Baseline Mode should be
available at instrument commissioning or soon thereafter.
We begin with a discussion of coordinate systems,
which are needed to understand the relationships between sky, focal plane
and detector.
This is followed by a description of the major calibration elements,
the major dependencies for each of these elements,
and general procedures for addressing each.
We next discuss the detector calibrations, imaging data and
spectroscopic data in turn, from the perspective of specific procedures
and database products necessary for calibrating each stream of data.
The final section covers routine diagnostic tests to monitor
system stability, e.g., optical alignments.
This document presumes a working knowledge of the DEIMOS instrument,
to be found in the Preliminary and Critical Design
Reports, the Software Preliminary and Critical Design Reports,
the Flexure Compensation System Report (TBD), and ??.
Next: 1 Glossary of Terms
Up: No Title
Previous: 9 Acceptance Suite
DEIMOS Software Team <deimos@ucolick.org>
1997-06-13T00:18:19