Haystack Observatory
The Haystack Observatory, located in Westford, MA, is an interdisciplinary research center focused on the advancement of radio science with applications to astronomy, geodesy, and atmospheric physics. The current priority of the astronomy program at Haystack is to develop large radio interferometric arrays of telescopes that will achieve high sensitivity and resolution needed for the study of the structure of our galaxy, the early Universe, and transient astronomical events. The astronomy research program is carried out under the auspices of the Northeast Radio Observatory Corporation (NEROC), a consortium of eleven educational and research institutions in the northeast. The primary objective of the geodetic research is to improve the accuracy of measurements of Earth's orientation parameters by enhancing the bandwidth of the observations through innovative instrumentation development. The current goal of the atmospheric research is to understand the impact of solar disturbances on the Earth's upper atmosphere through radar and optical measurements. An important component of the observatory's mission is to support the training of students by providing opportunities for them to link their education with research through the disciplines practiced at the observatory. The observatory receives financial support primarily from federal agencies including the National Science Foundation, the National Aeronautical and Space Administration, and the Department of Defense, as well as from industrial sources.
Instrumentation
The Haystack Observatory instrumentation consists of the following facilities:
- A 37-m diameter radio telescope used for astronomical observations and for radar measurements.
- An 18-m diameter radio telescope involved in geodetic measurements of the Earth's rotation parameters using very long baseline interferometry (VLBI).
- An 8-station wideband VLBI correlator used to process global geodetic and astronomical observations.
- A 2.5 MW UHF radar that utilizes two large antennas, 46 m and 67 m in diameter, to study the Earth's upper atmosphere using incoherent backscatter techniques.
- An optical observatory consisting of Fabry-Perot interferometers to measure winds in the Earth's upper atmosphere, and a lidar system with the 1.2-m Firepond telescope to measure temperature in the lower atmosphere.
Radio Astronomy
Haystack Observatory has been pursuing several initiatives associated with the development of large radio arrays for the future that will allow us to achieve very high sensitivity and open new areas of astronomical science. Emphasis has been placed during the past year on the scientific and technical considerations for such arrays, as well as on simulation and configuration studies. As a result, two of these array initiatives have matured to the level that funding will be in place to begin their implementation during the next year.
The first involves a Low Frequency Array (LOFAR) operating at 10(240 MHz using 100 stations distributed over 400 km and connected with optical fiber. LOFAR will allow the detection of radio sources at the milli-Jansky level with arc-second resolution, and will be the first fully digital radio telescope capable of observing with multiple independent beams. In this project led by Dr. Colin Lonsdale, Haystack staff are collaborating with the MIT Physics Department(Professor Jacqueline Hewitt , the Netherlands Foundation for Research in Astronomy, and the Naval Research Laboratory. The scientific projects of interest to the MIT and Haystack astronomers involve measurements of the structure of the universe at the early epoch of re-ionization and the detection of transients such as gamma ray bursts through their radio emission. Based on a successful proposal submitted in the past year to the NSF Information Technology Program, we expect to begin the detailed design of LOFAR starting in October 2001. Construction is expected to start after a three-year design phase which will include evaluation of several candidate sites in the U.S., the Netherlands, and Australia. It is our goal to establish a science center for LOFAR at MIT/Haystack to facilitate the scientific use of the instrument for our research goals as well as for the U.S. astronomical community.
The second array project was proposed by Alan Rogers for the detection of deuterium(a most sensitive indicator of the density of baryons which relates to the assessment of dark matter in the Universe. Detection of the deuterium line at a radio frequency of 327 MHz has been elusive due to inadequate sensitivity of available telescopes. Haystack's proposed approach is through the development of a sensitive digital receiver based on modern technology and the design of an 64-station array of dipole elements to be constructed at the Observatory in Westford. The proposal competed successfully under the NSF Major Research Instrumentation program, with cost-sharing support from TruePosition, Inc. which supports research at Haystack on the location of E911 calls from cellular phones based on a spin-off from VLBI technology. Prototyping of the antenna and receiver is expected to start in October 2001, with construction to follow in 2003.
Astronomical research work by Haystack staff has concentrated on the application of Very Long Baseline Interferometry (VLBI) at millimeter wavelengths using a global array of twelve radio telescopes to make high resolution observations of radio sources and study their structure and evolution. The significant scientific results that have emerged from this research in the past year included the first polarization images of two Active Galactic Nuclei at 3-mm wavelength, and the measurement of the intrinsic size of the compact source in the center of our galaxy.
VLBI observations of the total intensity and linear polarization of 3C273 and 3C279 at 3-mm wavelength (86 GHz) have been reported by the MIT-Center for Astrophysics post-doctoral researcher at Haystack, Dr. Joanne Attridge. The core of blazar 3C273 was found to be unpolarized while a peak polarization of 11 percent was measured in a jet component adjacent to the core. For blazar 3C279, peak fractional polarization of 26 percent was located between the core and the jet component. These observations revealed the complex magnetic field structures in the core and jets of these two blazars.
A direct measurement of the size of the compact radio source, Sagittarius-A, at the center of our galaxy is important since it helps discriminate amongst different emission mechanisms thought to operate in this source. In the mm-VLBI project led by Drs. Sheperd Doeleman and Alan Rogers, the results indicate a circular size of 0.18 milli-arcseconds for Saggitarius-A, consistent with extrapolations made from observations at longer wavelengths but revealing that we have not yet detected the intrinsic structure of the source as proposed by others. Measurements using longer baselines will continue in the next year with the aim of improving the accuracy of the size determination.
Instrumentation Development
The focus of the VLBI instrumentation development in the past year has been on increasing the signal bandwidth in the observations to enhance the sensitivity of our geodetic VLBI systems. The goal is to develop a data acquisition system capable of operating in an unattended mode at a rate of 1 Gbit/sec utilizing commercial off-the-shelf components. Under the leadership of Dr. Alan Whitney, a proof-of-concept demonstration was successfully completed in the past year based on the use of magnetic disks. Initial recording and playback at 0.5 Gb/s were demonstrated at an International VLBI workshop held at Haystack in May 2001 and attended by 75 researchers who are associated with the radio telescopes around the world. All major VLBI groups have endorsed the new Mk5 system due to its reliability and ease of operation. A development path for achieving 1 Gb/s and higher rates has been outlined, and a consortium of funding partners from the national and international community has been assembled to support this work at Haystack Observatory. The plans are to complete the development in 2002 with beta-versions to be released in 2003. Technology transfer to industry will then follow for the implementation of the Mk5 system worldwide.
A key element in the design of the Mk5 system is its ability to interface with high-speed wideband communication links. With the rapid expansion of fiber optic links across the U.S., Europe and Japan, real-time transmission of VLBI data from the radio telescopes to the correlator is now becoming feasible. The advantages of real-time data transmission include the ability to test experimental setups in the field by verifying data acquisition, reduction of delays in processing the data and elimination of tape-shipping costs, and enhanced bandwidth beyond that allowed through data recording. Haystack Observatory has been recently connected with a wideband fiber optic link through efforts at Lincoln Laboratory and MIT, and this allows us to transmit data from the Observatory in Westford to Cambridge, Lexington, and Boston, and then to the Washington D.C. area through DARPA's Bossnet system. This then provides a unique opportunity to begin the development of the real-time VLBI system(named 'e-VLBI' by Dr. Alan Whitney who leads this effort. Work has started on the equipment design for the first demonstration experiment, funded jointly by DARPA and NASA. This involves the acquisition of astronomical data using MIT's Westford radio telescope and the NASA telescope at Goddard Space Flight Center, both of which will be equipped with Mk5 systems, and the transmission of the data through Bossnet to the Haystack correlator for real-time processing. Following a successful demonstration, we plan to conduct tests with European and Japanese telescopes through the use of Internet2 and equivalent networks.
In a project led by Dr. Alan Rogers and supported by TruePosition, Inc., Haystack participated in field tests of a system aimed at the radio location of E911 calls from cellular phones using VLBI time-delay measurement techniques. The tests successfully demonstrated the accuracy of the system to locate such calls within the specifications set by the FCC in the harsh multipath environment in Manhattan, NY. Current plans call for further research on a system that uses angle-of-arrival measurements to support radio-location in rural areas. Readiness of the TruePosition system for implementation by cellular phone carriers will be determined in October 2001(a date set by the FCC.
Atmospheric Science
Major geomagnetic storms occurred during the past year, coincident with the peak in the solar cycle. As a result of two large solar coronal mass ejections July 14, 2000 and March 31, 2001, large perturbations occurred in the Earth's geomagnetic field and in the upper atmosphere and ionosphere, and produced auroral displays as far south as Florida and Texas. The MIT incoherent scatter radars at Haystack Observatory were promptly activated to make observations of the temperature, density, plasma drifts and neutral winds in the region from 100 to 1000 km. Large ion drift velocities and density gradients at 300-400 km altitude were observed by Dr. John Foster and his group during these intense storms, and electric fields of 100 mV/m were detected in the ionosphere(the largest ever recorded at our Observatory. At altitudes near 100 km, the radar observations revealed neutral wind velocities of 500 m/s compared to 50(100 m/s observed during quiet solar times. The winds were found to be northward in direction as a result of heat deposition by the aurora south of our site. These unique data sets form an important input to models of the Earth's upper atmosphere aimed at investigating the coupling between the Sun and Earth(a goal being actively pursued by NSF, NASA and the Air Force Office of Scientific Research.
Using the Rayleigh lidar system that was recently completed at the observatory, significant scientific results were obtained by Dr. Thomas Duck and his colleagues during the past year. The first measurement of a temperature inversion layer at mesospheric altitudes (~50-60 km) in the daytime was recorded, and the first direct evidence of a correlation between the amplitude of the temperature inversion and the intensity of acoustic gravity waves in the stratosphere (below 50 km) was obtained. These unique observations established a causal relationship between the dissipation of gravity waves at their breaking altitudes and the appearance of an inversion layer. The results help improve our understanding of the coupling between the lower and upper parts of the Earth's atmosphere, and fulfill the main goals of the development of the lidar system at the Observatory. The success of the unique daytime observations was achieved by the use of the unique narrow field-of-view 1.2-m Firepond telescope made available to our project by Lincoln Laboratory.
Educational Programs
The program to strengthen undergraduate education through research in radio astronomy using the MIT facilities at Haystack continued successfully, under the leadership of Dr. Preethi Pratap, the observatory's educational officer. A total of 135 students from 20 colleges within the NEROC consortium and elsewhere have utilized the observatory's 37-m telescope during the past year as part of courses, laboratory exercises and special projects, by either visiting Haystack or controlling the telescope remotely through the internet. An excellent illustration of a project carried out by an undergraduate is that of MIT student Ben Blount who used the telescope to search for radio emission from axions, under the guidance of Professor Leslie Rosenberg of the Physics Department, and recently published his results in the Astrophysical Journal.
Implementation of Haystack's small radio telescope (SRT), which consists of a 2-m antenna with a 1400 MHz receiver, also continued successfully during the past year. The SRT is designed as an introduction to radio astronomy at the undergraduate level. Haystack deployed 18 beta-units of the SRT at various NEROC colleges and other institutions, and the experience gained from these units has been valuable for completing the documentation and improving the operations of the system. Commercialization of the SRT was accomplished during the past year through CASSI(Custom Astronomical Support Services Inc.(a small business formed by Dr. Michael Cobb in southeast Missouri for the purpose of providing copies of our SRT to other interested colleges and groups. At present, Haystack is designing a digital receiver for the SRT to enhance its observational capabilities, and we are testing the usefulness of the SRT at the pre-college levels by working with high-school science teachers in the local area and making a trailer-mounted telescope available to them and their students.
Finally, Haystack Observatory continued its successful summer research internship program for undergraduates and for pre-college science teachers, with support from the NSF. Eight students recruited from across the nation and four teachers recruited locally have participated in the program during the past year. The students and teachers are mentored by members of the Haystack staff and participate in the Observatory's research projects in astronomy, atmospheric science and instrumentation development. A total of 16 major public outreach activities including two community open-house events were conducted at Haystack during the past year, and about 1000 pre-college students toured the facilities with their teachers as part of our efforts to excite young people about science and engineering.
Infrastructure and Administrative Changes
A new building addition to the Haystack Observatory, consisting of 18 offices and a conference room, was completed in June 2001 to house the Atmospheric Sciences Group. This will provide a better working environment for the staff who were housed in temporary trailers attached to a small building. With the close proximity of the atmospheric and astronomical sciences staff, it is expected that some synergistic interests in common projects such as LOFAR will develop, thus strengthening the overall Observatory research program.
During the past year, the administrative support functions for the MIT facilities at the Westford site have been integrated together under one MIT department(Haystack Observatory. Previously, the budgeting and facility maintenance functions, including support of the Lincoln Laboratory projects in Westford, were carried under two separate departments, Haystack Observatory and Millstone Hill. With the move of the Atmospheric Sciences Group to Haystack and the integration of the Lincoln Laboratory space surveillance activities under a single group, the efficiency and accountability for the entire site administrative support have been enhanced as a result of this integration.
More information about the Haystack Observatory research and education programs can be found online at http://www.haystack.mit.edu/.