Millstone Hill
Encyclopedia
The Millstone Hill Steerable Antenna, or MISA, is a fully steerable dish antenna, 46 meters in diameter, designed by the Stanford Research Institute (SRI) in 1959. It is currently located at MIT Haystack Observatory
in Westford, Massachusetts. It was originally installed at the Sagamore Hill Radio Observatory
in Hamilton, Massachusetts
in 1963. The antenna operated at that location until 1978, at which time it was relocated to Millstone Hill. Since that time it has been primarily used as a UHF radar
antenna to provide measurements of the near space
environment using the incoherent scatter
radar
technique. It is one of two surviving dish antennas of this type in the world with the other antenna being located at the Stanford University
radio science field site in Stanford, California
. MISA is used to provide wide radar coverage in latitude and longitude.
MISA is a broad-based observatory capable of addressing a wide range of atmospheric science investigations. The incoherent scatter radar facility at Millstone Hill has been supported by the National Science Foundation
since 1974 for studies of the Earth's upper atmosphere and ionosphere
. During this time the facility has evolved from a part-time research operation sharing radar cooling and power supply elements with the M.I.T. Lincoln Laboratory
Millstone satellite tracking radar, to a separately funded, operationally independent system dedicated to upper atmospheric research. The scientific capability of the Millstone Hill facility was greatly expanded in 1978 with the installation of a fully steerable 46 meter antenna to complement the 67 meter fixed zenith
pointing dish.
The favorable location of Millstone Hill at sub-auroral latitudes combined with the great operational range afforded by the steerable antenna permit observations over a latitude span encompassing the region between the polar cap and the near-equator
ial ionosphere. Since 1982 the Haystack Observatory Atmospheric Sciences Group has been supported for operating the Millstone Hill research radar as a part of the incoherent scatter radar chain and for associated studies of the auroral and sub-auroral ionosphere and thermosphere
. The meridional radar chain extends from Sondre Stromfjord, Greenland
through Millstone Hill at mid-latitudes, beyond Arecibo
at low latitudes, to the Jicamarca facility at the magnetic equator in Peru
. The radar chain forms an integral part of the NSF-supported CEDAR (Coupling, Energetics, and Dynamics of Atmospheric Regions) observing network and Millstone Hill observations and analysis have contributed extensively to the successes of the CEDAR initiative.
The Millstone Hill Radar uses Thomson backscatter
from ionospheric electron
s to deduce height- and time-resolved plasma drift velocities, electron and ion temperatures, electron densities, ion composition, and ion-neutral collision frequencies. These parameters provide further information about the neutral gas, neutral temperatures and winds, and electric fields present in the medium. The incoherent scatter technique provides observations of many of these parameters over an altitude range extending from less than 100 km to a thousand kilometers or more. Methods have been developed that allow these measurements to be made with an altitude resolution of hundreds of meters. The complete steerability of the radar allows horizontal gradients and structure to be examined along with vertical variations.
Haystack Observatory
Haystack Observatory is a group of astronomical observatories owned and operated by Massachusetts Institute of Technology. It is located in Westford, Massachusetts . It is the home of the Millstone Hill Observatory....
in Westford, Massachusetts. It was originally installed at the Sagamore Hill Radio Observatory
Sagamore Hill Radio Observatory
- Location :Sagamore Hill, Hamilton, Massachusetts, USA The Sagamore Hill Solar Radio Observatory is a ground-based solar radio telescope observatory located in Hamilton, Massachusetts that operates on a daily basis to obtain scientific observations of the sun. It is a functional component of the...
in Hamilton, Massachusetts
Hamilton, Massachusetts
Hamilton is a town located in the eastern central portion of Essex County in eastern Massachusetts. It is primarily a suburban bedroom community, most commonly known for its equestrian estates...
in 1963. The antenna operated at that location until 1978, at which time it was relocated to Millstone Hill. Since that time it has been primarily used as a UHF radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
antenna to provide measurements of the near space
Near space
Near space is the region of Earth's atmosphere that lies between 65,000 and 325,000–350,000 feet above sea level, encompassing the stratosphere, mesosphere, and thermosphere. A more understandable definition would be above where a commercial airliner flies but below the realm of an orbiting...
environment using the incoherent scatter
Incoherent scatter
Incoherent scattering is a type of scattering phenomenon in physics, which may involve various particles, such as neutrons or photons.One application is a ground-based technique for studying the Earth's ionosphere. A radar beam scattering off electrons in the ionospheric plasma creates an...
radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
technique. It is one of two surviving dish antennas of this type in the world with the other antenna being located at the Stanford University
Stanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
radio science field site in Stanford, California
Stanford, California
Stanford is a census-designated place in Santa Clara County, California, United States and is the home of Stanford University. The population was 13,809 at the 2010 census....
. MISA is used to provide wide radar coverage in latitude and longitude.
MISA is a broad-based observatory capable of addressing a wide range of atmospheric science investigations. The incoherent scatter radar facility at Millstone Hill has been supported by the National Science Foundation
National Science Foundation
The National Science Foundation is a United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National Institutes of Health...
since 1974 for studies of the Earth's upper atmosphere and ionosphere
Ionosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
. During this time the facility has evolved from a part-time research operation sharing radar cooling and power supply elements with the M.I.T. Lincoln Laboratory
Lincoln Laboratory
MIT Lincoln Laboratory, located in Lexington, Massachusetts, is a United States Department of Defense research and development center chartered to apply advanced technology to problems of national security. Research and development activities focus on long-term technology development as well as...
Millstone satellite tracking radar, to a separately funded, operationally independent system dedicated to upper atmospheric research. The scientific capability of the Millstone Hill facility was greatly expanded in 1978 with the installation of a fully steerable 46 meter antenna to complement the 67 meter fixed zenith
Zenith
The zenith is an imaginary point directly "above" a particular location, on the imaginary celestial sphere. "Above" means in the vertical direction opposite to the apparent gravitational force at that location. The opposite direction, i.e...
pointing dish.
The favorable location of Millstone Hill at sub-auroral latitudes combined with the great operational range afforded by the steerable antenna permit observations over a latitude span encompassing the region between the polar cap and the near-equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
ial ionosphere. Since 1982 the Haystack Observatory Atmospheric Sciences Group has been supported for operating the Millstone Hill research radar as a part of the incoherent scatter radar chain and for associated studies of the auroral and sub-auroral ionosphere and thermosphere
Thermosphere
The thermosphere is the biggest of all the layers of the Earth's atmosphere directly above the mesosphere and directly below the exosphere. Within this layer, ultraviolet radiation causes ionization. The International Space Station has a stable orbit within the middle of the thermosphere, between...
. The meridional radar chain extends from Sondre Stromfjord, Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
through Millstone Hill at mid-latitudes, beyond Arecibo
Arecibo
Arecibo may refer to:*Arecibo, Puerto Rico, a municipality located by the Atlantic Ocean*Arecibo Observatory, a very sensitive radio telescope located approximately south-southwest from the city of Arecibo...
at low latitudes, to the Jicamarca facility at the magnetic equator in Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
. The radar chain forms an integral part of the NSF-supported CEDAR (Coupling, Energetics, and Dynamics of Atmospheric Regions) observing network and Millstone Hill observations and analysis have contributed extensively to the successes of the CEDAR initiative.
The Millstone Hill Radar uses Thomson backscatter
Backscatter
In physics, backscatter is the reflection of waves, particles, or signals back to the direction they came from. It is a diffuse reflection due to scattering, as opposed to specular reflection like a mirror...
from ionospheric electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s to deduce height- and time-resolved plasma drift velocities, electron and ion temperatures, electron densities, ion composition, and ion-neutral collision frequencies. These parameters provide further information about the neutral gas, neutral temperatures and winds, and electric fields present in the medium. The incoherent scatter technique provides observations of many of these parameters over an altitude range extending from less than 100 km to a thousand kilometers or more. Methods have been developed that allow these measurements to be made with an altitude resolution of hundreds of meters. The complete steerability of the radar allows horizontal gradients and structure to be examined along with vertical variations.