We should be able to re-create or re-consider any data analysis of DEIMOS images using the archived information; and we should be able partially to automate the process of data reduction -- an important goal when we consider the volume of data this instrument is likely to produce. For better engineering support, we should be able to analyze instrument history; engineers as well as astronomers should be able to make complex statistical and quantitative queries against a complete history of the instrument's performance and status.
We should also provide a mechanism for the publication of data acquired using DEIMOS, with an easy interface enabling astronomers and the general public to browse (or submit complex analytical queries to) the database of information described above as well as a library of published images.
Our design goal is therefore to provide an information management infrastructure and user toolset enabling:
Note: We are using the term "meta-data" in the context of the science data, not of the database internals. In this PDR document, "meta-data" will be used to mean all environmental, inventorial, historical (etc.) data relevant to the science and calibration images acquired using the instrument. It will also include all those database constructs more restrictively defined by database designers as "meta-data," i.e. data dictionary, access control, and similar tables.
Physical Components
Certain components of the instrument have innate or relatively static
characteristics which affect the performance of the instrument as
a whole. These static, physical components should be catalogued and
described in sufficient detail to explain or analyze their impact
on the quality of acquired data.
Slit Masks
A slit mask is a metal blank which has been perforated with
small apertures, precisely machined according to a "map" of an
area of the sky containing objects
of interest to the astronomer. The list of objects, their mapping
(or not) to apertures on the mask, and the physical
geometry of the mask, are all very important to the observing
process. A large library of slit masks will rapidly accumulate,
and we should be able to distinguish each mask uniquely,
to retrieve its design and purpose, and to recreate it if for
some reason it is lost or damaged. The special pre-cut stock
for fabricating slit masks must be inventoried as well, even
before it is made into functional masks. See
Figure 9.2.7 for a semi-detailed sketch of a database schema
for describing slitmasks, and Figure 9.2.6
for a sketch of the slitmask production process.
Appendix 9.10.E may be helpful in understanding
schema diagrams; it contains descriptive text about Figures
9.2.7 and 9.2.9 (see below).
CCDs
CCD chips are used in the imaging mosaic, the guide camera(s), and
the flexure compensation system (FCS). Each of these chips has a
provenance and manufacturing history relevant to its performance in
the instrument. See Figure
9.2.10 for a sketch of the CCD production process.
The implementation of a complete database system for tracking and managing the
CCD production process has already been initiated at UCO/Lick
independently of the DEIMOS project; the DEIMOS project
underlines the need for such a system and may accelerate its
development. See Figure 9.2.9 for a semi-detailed
sketch of a schema for describing CCDs; Appendix 9.10.E
offers explanatory text which may be helpful in understanding drawing 9.2.9.
Other Components
Other physical components of the instrument requiring online documentation
include: filters, gratings, lenses, mirrors, and lamps. Each of these
has a set of static (descriptive) attributes, and a set of possible events
(such as cleaning, alignment, etc) which should be logged. See
Figure 9.2.8 for a sketchy schema describing
these physical components.
Operation of the Instrument
Logging of environmental and operating conditions throughout
each night is essential, whether we are engineers seeking reasons
for vagaries of instrument and telescope performance or astronomers
seeking to understand our acquired data. A consistent and complete log
of such information should be maintained indefinitely for
cross-reference to trouble logs as well as to phenomena and
artifacts in observed data.
These operational data are more dynamic than catalogs of components and their characteristics. The operational log should record all rapidly-changing status information (changes during the night, during the run, or between runs); this includes but may not be limited to:
Acquired Data
An historical record of data acquired at the telescope, together with
all meta-data which could affect the quality or interpretation of
the acquired images, can be of enormous value to the original observer
and to later researchers. The meta-data should be published immediately,
but the acquired data (and slit mask definitions)
may be considered confidential for some period of months or
years; possibly this period is determined by the initial conditions of the
construction grant. Therefore some mechanism for control over publication date must be
provided. These "semi-private" data include but are not limited to:
de@ucolick.org