The McMath-Pierce facility is the world's only large solar telescope without an entrance window, thus giving it unique access to the solar infrared spectrum beyond 2.5 micron. NSO, like NOAO, has concentrated its in-house instrumentation program on the 1--5 micron region. The McMath-Pierce also carries out observations in the important 12-micron region through collaboration with NASA's Goddard Space Flight Center.
NSO is taking full advantage of NOAO's investment in the Aladdin array development project. With 16 times as many pixels, higher quantum efficiency, lower read noise, and better immunity from electronic interference, a 1K x 1K Aladdin-based camera will be superior to the current 256 x 256 camera in every respect and will enable new types of scientific observations, such as vector magnetograms of weak field concentrations. The new camera will be used for exploratory imaging and spectroscopy as well as with the existing Near Infrared Magnetograph. Implementing and demonstrating the scientific value of a fast, large-format infrared camera is an important component of NSO's preparation for an IR-capable Advanced Solar Telescope.
With a commitment from NOAO for a science-grade 1K x 1K array in place, a Request for Proposal for the array controller, cryostat, and optics will be issued early in FY 2000.
While two new proposals have been submitted to the NSF computing division for further development of the NSO Digital Library, FY 1999 marks the last year of NSF Space Weather Program funding for the NSO Digital Library development. Since the bulk of the initial development was completed in FY 1998, FY 1999 was devoted to fine-tuning and maintenance of the system, as the user community became aware of the resource. Currently, the 300-disc CD-ROM jukebox holds complete sets of 44 discs of non-proprietary FTS transformed spectra, 64 discs of FTS interferograms, 44 discs of KPVT 512-channel magnetograph data, 56 discs of KPVT spectromagnetograph data, and a partial set of 18 discs of Sac Peak Evans Facility spectroheliograms for a total of about 158 GB of on-line storage.
The usage of the CD-ROM jukebox system increased by a factor of three in FY 1999 as compared to FY 1998. Outside users downloaded a total of 18,083 files from the jukebox in the period of 1 August 1998 to 31 July 1999. This is to be compared to the total of 6,000 for the same period one year earlier. Access via the user interface contributed 619 files of the total for FY 1999.
The Adaptive Optics project, described earlier in the NSO Science Section, continues to make remarkable progress. The low-order system is now available for all users on a shared-risk basis. Collaborations with the AO group are strongly encouraged.
Two Spectral Instruments 1K x 1K CCD cameras were recently purchased and will be available to users by FY 2000. The SITe detectors are thinned back-illuminated providing outstanding quantum efficiency. The readout rate is 850 kHz with data recorded to DLT, hard disk, or exabyte.
The dual Fabry-Perot (FP) filter system for visible wavelengths is nearly complete and will become available to users during FY 2000. This system combines a 60 mÅ passband and a <20 mÅ passband FP with a set of narrow (3--4Å) blockers to provide a tunable narrow band filter with high transmission, capable of tuning at very fast speeds.
A second narrow band filter optimized for the near infrared from 1.1--1.7 m is currently available for users. It consists of two 50 mm aperture Fabry-Perot Etalons in tandem, which can be tuned from about 1.1 to 1.7 m. One of the FP is used as an order selector with a FWHM of 1.7Å and a free spectral range of 39.4Å at 1.56 m. The second FP provides narrow-band imaging. It has a FWHM of 113 mÅ and a free spectral range of 5.225Å. The order selecting and narrow-band Fabry-Perots have transmissions of 83% and 78%, respectively. We also have a blocking filter with a 47.6Å full width at half maximum (FWHM) centered on 1.5652 m and a transmission of 91%. The system has been combined with polarization optics and the NSO near-IR cameras to obtain weak field vector magnetograms.
The Cambridge Research and Instruments electrograph has recently been re-installed at the NSO/SP 40 cm coronagraph to carry out a two year program of measurements around the peak of solar activity. The experiment is designed to measure electric fields predicted in current sheets in coronal flares, post-flare loops, and quiet prominences. Observations taken with the electrograph in 1993 and 1994 yielded two main results: (1) r.m.s. upper limits in 9 quiet prominences of Et < 2--5 V cm-1 for the component of the electric field transverse to the line of sight; and (2) evidence for an electric field of E ~ 35 V cm-1 oriented approximately parallel to the magnetic field in a flare surge. The main objectives are (1) to improve the statistics on prominence measurements; (2) to obtain more measurements in flares; and (3) to obtain new results on post-flare loops.
ISOON (Improved Solar Observing Optical Network) is a USAF-funded project being conducted at NSO/SP. When completed, ISOON will consist of a network of telescopes placed at four sites around the world to provide 24-hour coverage of solar activity. ISOON is in a transition phase between development and production. Having successfully completed a critical design review in January 1999, the effort is currently focused on completing design details and adapting the existing SOON hardware to the ISOON application. All major hardware components, including dual 15-cm Fabry-Perot filters, have been purchased, and the software for data acquisition, processing, telescope control, and data display and analysis is about 50% complete. The optical components have been tested and shown to be of excellent quality. Installation of the first unit (at Holloman AFB) is expected to occur in early fall 2001. Three additional installations will follow at about six-month intervals. ISOON will provide 24-hr coverage with 2K x 2K images in H (every minute), continuum (hourly), and magnetograms (every 3 hours). There are plans to archive the data, with free access to users in near real time.