E. Jenkins, P. Zucchino and M. Reale have completed their modifications and testing of the Interstellar Medium Absorption Profile Spectrograph (IMAPS), scheduled to fly on its second ORFEUS-SPAS mission from a Shuttle launch in November 1996. IMAPS is an objective-grating spectrograph that records the spectra of bright stars over the wavelength interval 950-1150A at a resolving power of about 150,000. Approximately 50% of the observing time for IMAPS will be available to guest observers who submitted winning proposals to the US and German space agencies, NASA and DARA.
D. Spergel is part of a Princeton/Goddard collaboration led by C. Bennett (GSFC) to build the MAP satellite. NASA has selected MAP as the next astrophysics MIDEX. It will map the microwave background fluctuations across the entire sky at an angular resolution of better than 20 arcminutes. MAP is scheduled for launch late in the year 2000.
The Sloan Digital Sky Survey effort at Princeton has included both construction of the giant CCD drift-scan camera for the 5 band imaging survey as well as development of the photometric pipeline for automatic processing of the multiband imaging data. J.E. Gunn has tfor the past three years been primarily concerned with various aspects of the Sloan Digital Sky Survey. He is currently project scientist for the project and as well is the principal investigator responsible for the construction of the large multi-CCD imaging camera for the survey.
The development of the photometric pipeline software for automatic reduction of the imaging data of the Sloan Digital Sky Survey (SDSS) has continued at Princeton by a group consisting of R. Lupton, N. Ellman, M. Richmond, J. Gunn and G. Knapp. Some code has also been written by T. Quinn (U. Washington).
The photometric pipeline's tasks include the selection of stars which will be used to calibrate the flux densities, correction of the data for cosmic rays and CCD defects (such as bad columns), flattening, determination of sky levels, finding objects, combining observations of an object in all five filters, measuring the brightness, position, size and shape of the objects, deblending objects with overlapping images, and extracting from the corrected imaging data the image of each object.
The photometric code has been successfully ported to the hardware platform which will be used to run the survey and has been successfully integrated with the pipelines which provide the photometric and astrometric calibration. Most of the coding is finished (deblending remains to be completed) and the software has been extensively tested using detailed simulations of the sky made by D. Weinberg (Ohio State), M. Doi (University of Tokyo) and B. Yanny (Fermilab). Independent tests have also been carried out of much of the software by N. Yasuda, K. Shimasaku, M. Fukugita and M. Doi (Universities of Tokyo and Kyoto). Integration with the Operational Data Base is well underway. The use of the photometric outputs for spectroscopic target selection has also been evaluated, as has input to the science data base.
Princeton software scientists have also contributed to other parts of the project. Richmond has made extensive contributions to the monitor telescope data reduction pipeline, which reduces the photometric calibration data and passes the results to the photometric pipeline, and to the acquisition and reduction of photometric calibration data. He has also participated in the development of the operational data base. Lupton and Gunn have contributed to the data acquisition software, and Lupton has worked on the operating system and on design of the science data base.
The SDSS hardware comprises several major subsystems, responsibility for which is spread over most of the participating institutions. The current schedule calls for installation of all subsystems on Apache Point in November 1996. It is anticipated that several months subsequently will be required to iron out system problems and to tune the various subsystems for peak performance as a system. The major subsystems are:
Structures and Support Services at APO
This is primarily the responsibility of the APO staff. All the buildings are finished, and all the road work has been done. One major item, for which Princeton is responsible, is the construction of a clean room for servicing the camera.
The Telescope and its Mounting
The telescope system is primarily the responsibility of the University of Washington, with the major subcontract for construction handled by L&F Industries in Los Angeles. Fermilab has considerable responsibility for the control system.
The telescope is on the mountain, assembled and working in a rudimentary way. Since it will not be working in a conventional dome, light and wind protection are afforded by a novel wind baffle. The instrument also has quite complex light baffles to accomodate its very wide field. The drives have been measured, and represent the most accurate system yet achieved on any telescope of any size.
Fermilab has responsibility for the control system and a large number of scientists and engineers are currently working on it intensively. The system is basically straightforward, but the accuracy required in order to meet the goals of the project (and to utilize the superb accuracy of the mechanical components) is not easy to achieve.
The Optics
The University of Washington has contractural responsibility for the optics, which were done by several vendors. The primary, at The University of Arizona Optical Sciences center, was finished in June, and meets specifications except for a slight large-scale warp which can be taken out by small forces built into the mirror mounting system. The secondary, figured by the Mirror Lab of the University of Arizona and tested by a revolutionary new technique for characterizing these classically very difficult-to-test convex mirrors, exceeds specification by nearly a factor of two. The very complex aspheric camera corrector, which forms the substrate for the camera assembly, was delivered by Don Loomis in the early spring and is superbly done, as is the very strongly curved spectroscopic final corrector, done by Tinsley and delivered in July. The common (Gascoigne) corrector is under construction by Contraves and is scheduled for a mid-October delivery.
The Monitor Telescope
The MT is a 0.6m telescope which will work alongside the 2.5 meter in order to provide brightness standards and to characterize the transmission of the atmosphere. It is working, taking data, and in the process of finalization of its software and a final rework to correct some deficiencies in its electronics.
The Spectrographs
The spectrographs are being constructed at Johns Hopkins, and their CCD cameras and electronics at Princeton. Both systems are substantially finished; a working camera has been delivered to JHU, and tested with the Fermilab data acquisition system.
The Camera
Princeton is constructing the CCD survey camera. Final assembly of the instrument is underway. Essentially all of the mechanical parts have been delivered; all of the CCD detectors have been received, tested, characterized, and mounted to their precision holders. The major electronic circuit boards are all finished and have been fully populated and tested. An electronics team consisting of J. Gunn, G. Pauls (Princeton), C. Rockosi (Chicago), M. Sekiguchi (National Observatory, Japan), F. Harris (Naval Observatory), J. Brinkman (APO), and D. Sandford (Chicago) converged in Princeton this summer and substantially finished the very complex electronics system. The mechanical part of the camera is being done by J. Gunn, M. Carr (Princeton), M. Sekiguchi (Japan), with machining assistance by B. Elms (Princeton). Assembling the camera to the tolerances designed has proven to be even more painstaking than originally envisioned. The camera is scheduled for installation at Apache Point in November 1996.