1 Introduction and Overview

1.1 Highlights of CDR Document

This section provides an overview of the CDR document which consists of the following five parts:

• I. Introduction and Overview
• II. Subsystem Designs
• III. DEIMOS Calibration
• IV. Flexure Compensation
• V. Budget and Schedule

Since the document is very long, we list here the sections to which we would particularly like to direct the review board's attention. We hope that all board members will have a chance to read these essential sections prior to the CDR.

• Part I, Appendix A: Contains an updated and detailed response to the report of the DEIMOS Software PDR Review Board. It describes the specific actions we have taken in response to the board's recommendations and provides a comparison of projected versus actual progress over the interval between the PDR and CDR. This appendix also highlights several critical personnel and management issues which urgently need to be resolved; see I.A.4.2. A summary of this appendix is provided in section I.2.1.
• Part I, Chapter 3: Describes those areas of the DEIMOS system in which we have a solid proof of concept for the underlying software and/or hardware components. In many cases, these proofs are in the form of fully functional software tools (operating within a well-defined software infrastructure) that have been successfully used to complete and document the software designs presented in this volume.
• Part I, Chapter 4: Describes areas of risk for which neither a detailed design nor proof of concept yet exists. Contingency plans for the Image Display subsystem are discussed, and an abbreviated set of functional requirements for the Flexure Compensation and Calibration subsystems is provided. (A more detailed discussion of the Calibration and Flexure Compensation subsystems is provided in Parts III and IV, respectively.)
• Part II, Chapter 1: Describes the design of the software and operating procedures for the slitmask design and fabrication subsystem. This design has evolved significantly from what was presented at the PDR. Since the inventory and production control aspects of this subsystem are ones that we have not faced in previous instruments, these aspects should be afforded careful review.
• Part II, Chapter 7: Describes the information management (database) subsystem, which is integral both to the operation of the overall instrument and to the design and documentation of all of the DEIMOS subsystems (including itself). This chapter addresses various concerns about this subsystem that were raised at the PDR, including the concern that the database component per se will delay the project schedule or consume more than its share of resources. This chapter illustrates that the database subsystem now has a more limited and well-defined scope and that so far it appears to be ahead of the other major instrument subsystems: the design of this subsystem is nearly complete, the implementation of most of its components is quite advanced, and many of its components are already operational. The various documentation products that are automatically generated by this subsystem offer solid proof of the utility of its design and its cost effectiveness.
• Part V: Describes the DEIMOS software budget and schedule. This part was not ready in time for the pre-CDR distribution of documents, but will be presented at the CDR. A significant block of time is being allocated for its presentation and subsequent discussion at the CDR.

The remaining portions of this CDR document are less important. In particular, parts III and IV consist of supplementary material:

• Part III is intended to become a separate document on DEIMOS Calibration, but it is not yet complete. Its contents are summarized in section I.4.3 and it is included in draft form for reference only. It defines the procedures and mathematical relationships required for the calibration of DEIMOS data but does not specifically address the detailed design of the calibration software. Accordingly, Part III is a preliminary step in defining the functional requirements for that subsystem. (Since implementation of pipeline data reduction is a goal rather than a commitment, it will likely not occur until much closer to or even after instrument commissioning. Recall that the DEIMOS software effort is budgeted to continue for 2 years beyond first delivery.) A complete detailed software design of this subsystem will not commence until later in the project. However, the material in Part III indicates how well the requirements of this subsystem are understood, and the magnitude of the design and implementation task which remains. An understanding of these points is needed to assess the budget and schedule impacts of implementing pipeline data reduction.
• Part IV is intended to become a separate document on the Flexure Compensation (FC) Subsystem, but it also is not yet complete. Its contents are summarized in section I.4.2 and it is included in draft form as part of the CDR document to serve as a preliminary set of functional requirements for this subsystem. However, the FC subsystem is a required part of the instrument, so the detailed design of its software must proceed now. To date, the overall FC system (optical, mechanical, electronic, and software) has not been subject to any detailed independent review. This software CDR represented the first opportunity to review much of the material contained in Part IV, and while the completed portions of this FC document do not specifically focus on software, they do indicate the level to which the requirements of this subsystem are understood, and the magnitude of the design and implementation task which remains. We recommend that the overall FC system be reviewed at a later date.

In addition to the five parts of this CDR document, we have also produced a preliminary draft of Lick Observatory Technical Report ???: The DEIMOS Keyword and Database Dictionary. This report (commonly referred to as LOTR ??? or ``The Dictionary") provides a dictionary defining all of the DEIMOS keywords and database tables. Example pages from this dictionary are included in section I.3.4 of this document. However, due to its large size, we are not including LOTR ??? as part of the pre-CDR distribution of documents to the review board. Copies of LOTR ??? will be available for inspection at the CDR. An on-line copy of LOTR ??? will be available on or before June 13 via the WWW at the following URL:

http://www.ucolick.org/ deimos/lotrxxx.html

For those reviewing this dictionary, remember that it is automatically generated from the data contained within the various tables of the DEIMOS database, using the document generation tools which are described in section I.7.1.1. Not all data are complete, but the dictionary currently represents approximately 80% of its finished equivalent.

1.2 Overall System Summary

This section provides a global overview of the DEIMOS software system. It includes two diagrams showing all of the major subsystems and their interconnectivity (see Figures 1.1 and 1.2).

The DEIMOS system consists of the following major software subsystems, which are described in the indicated sections of this report.

• Mask Design: Part II, Chapter 1
• Mast Fabrication: Part II, Chapter 1
• DataBase: Part II, Chapter 7
• Mask Management: Part II, Chapter 1, Section 5
• Spectrograph Control: Part II, Chapter 3
• Header Collection: Part II, Chapter 4 (available at CDR)
• Science Data Capture: Part II, Chapter 4 (available at CDR)
• Image Display: Part II, Chapter 6
• STB: Existing system at Keck
• Pipeline Reduction: Part III
• Mask Alignment: Part II, Chapter 2
• Detector Control: Part II, Chapter 4 (available at CDR)
• DCS and Guider: Existing system at Keck
• Rotator Control: follows model of HIRES rotator (existing system)
• Flexure Compensation: Part IV
• Documentation Facility: Part II, Chapter 7
• Calibrate Spectrograph: Part III
• Logging Facility (KTLwatch): Part II, Chapter 8
• Engineering Data Visualization: Part I, Chapter 3, Section 2
• KTL User Tools: Part I, Chapter 3, Section 2, plus existing KTL UIs

 
Figure 1.1:   Overall system data flows

 
Figure 1.2:   KTL User Tools data flows

1.3 Changes to the Instrument

  The basic optical properties and capabilities of DEIMOS were described in Chapter 2 of the Software PDR Report http://www.ucolick.org/ deimos/swpdrtc.html presented on March 22, 1996. We list here the significant changes that have occurred since then that are relevant to software development.

• The final choice of CCDs has not been made, but the probable properties are better known, as discussed at the recent Detector/Controller CDR held on May 20, 1997. Copies of that report are available. A summary is given here in Part I, Chapter 2.7.
• The slitmasks   are now flat sheets of aluminum as carried in the slitmask cassette holder and are deformed to the curvature of the focal plane when inserted. The curved rigid holders have been eliminated. As a result we can now carry 12 slitmasks plus one longslit, an increase of 3 slots. Mounting and handling will be greatly simplified.
• The TV CCD   is a Photometrics 1K 1K SITe chip with 24 pixels, a scale of 02 px , and a total FOV of 33. The Photometrics camera looks at the telescope focal plane in staring mode. The visible focal plane is divided into two parts. One area is covered by a curved mirror permanently mounted in the telescope focal plane beside the slitmask area. This mirror is always visible regardless of whether the slitmask is in or out and provides offset guider capability when objects are not visible on the slits (e.g., during direct imaging). The dimensions of the offset guider area are . The remaining area of the TV FOV images either the cylindrical slitmask or a spherical mirror with a long slit, depending on which is inserted. The long slit is located 45 off axis from the center of the telescope focal plane. The dimensions of the imaged slit area are . The entire long slit area is unvignetted in the TV by virtue of its spherically curved mirror. Because the slitmask is cylindrical rather than spherical, objects will be visible only in a strip approximately 30  wide surrounding the longslit. However, the top surface of the masks is reflective, and it should be possible to place objects directly into the slitlets using the TV.
• The   grating slide still has slots for the imaging flat mirror plus three gratings. However, there is now room for only one -in grating (in Position 1), as Position 3 has been trimmed to accept only -in gratings to simplfy its encoder design.
• The option of tilting all grating positions to the flat mirror imaging angle has been retained, as it appears likely that notch mirrors for narrow-band imaging can be fabricated, giving DEIMOS a narrowband imaging capability that is otherwise not possible. Extra interlock hardware and software is needed to prevent collisions when grating slots are tilted to the mirror positions. ??True?
• The stated image stability goal of 0.25 px rms in each coordinate may not be achieved despite the Flexure Compensation system owing to thermal changes in the camera plate scale. These may cause image motions (contraction, expansion) of a few pixels at the edge of the detector if not successfully compensated passively in the thermal design of the camera lens barrel. Residual motions of this magnitude would have adverse implications for flat-field accuracy and wavelength stability, as described in Part I, Chapter 4.3 and Part III of this report.
• The slitmask milling machine has been received and debugged. It operates successfully.
• The SDSU-2 controller has been received and tested. It meets our needs, as described in the recent Detector/Controller CDR, held on May 20, 1997. Copies of that report are available.
• A   barcode reader has been added inside the spectrograph to read the IDs of slitmasks after the masks are loaded. These IDs are checked against plan and then loaded into the instrument control program and database.
• Remote observing   from Keck Headquarters at Waimea has been demonstrated using LRIS in multislit mode and is highly efficient, including slitmask alignment. Our default plan for DEIMOS after instrument commissioning is to observe remotely from Headquarters.