Millstone Hill Geospace Facility
The Millstone Hill Geospace Facility (MHGF) is owned and operated by the Massachusetts Institute of Technology (MIT) and is located in Westford, Massachusetts, at the Haystack Observatory complex. MHGF comprises a scientific and technical team of people and a cluster of radio, radar, and distributed instruments.
MHGF comprises the following three main elements.
Millstone Hill UHF incoherent scatter radar system
The current centerpiece of the Millstone Hill facility is its high-power, large-aperture incoherent scatter radar (IS radar) facility. This radar system consists of two 2.5 MW UHF transmitters, a fully steerable 46 m diameter antenna, and a fixed zenith directed 68 m diameter antenna. The Millstone UHF radar was built in 1958 as an MIT Lincoln Laboratory UHF ballistic missile and satellite tracking prototype radar. Its capabilities for ionospheric science were exploited in the early 1960s for pioneering incoherent scatter radar experiments. The facility has subsequently evolved a set of comprehensive and multi-instrument diagnostic capabilities for ionospheric and atmospheric investigations. Since 1974, the US National Science Foundation has supported Millstone Hill as the American longitude sector mid-latitude/sub-auroral IS radar Geospace Facility. The steerability of the Millstone Hill IS radar provides a unique capability for ionospheric observations of the full extent of mid-latitude, sub-auroral, and auroral features and processes.
For nearly 6 solar cycles, Millstone Hill’s location (42.6 ̊ geodetic latitude; 288.5 ̊ geodetic longitude; 54 ̊ magnetic latitude) has made it an enabling anchor for mid-latitude and sub-auroral science in the important plasmasphere boundary layer (PBL) [Carpenter and Lemaire, 2004]. The availability of wide field, full altitude plasma profiles within the PBL using incoherent/Thomson scatter radar has led to many fundamental discoveries of complex Geospace coupling phenomena. Important processes that are especially prominent in Millstone Hill data covering the American longitude sector include storm enhanced density (SED) plumes [Foster, 1993], sub-auroral polarization streams (SAPS) [Foster and Burke, 2002], and traveling ionospheric disturbances (TIDs) [e.g. Tsugawa et al., 2007]. Observations of these processes are central to a system-scale view of ionospheric and plasmaspheric variability and plasma transport, affecting Sun-Earth coupling processes such as dayside reconnection [e.g. Walsh et al., 2014] and relativistic particle acceleration [Foster et al., 2016]. The long-term MHGF IS radar-based data record, extending back to the late 1960s and made available to all through the Madrigal Geospace data system, provides climatological and long-term trends for secular upper atmospheric change (long term trends).
Millstone Hill observations are at the center of an expanding network of distributed instrumentation [total electron content, mid-latitude ionospheric convection patterns, distributed software radio sensors, magnetometers, passive optics], advancing observational knowledge of geospace processes and their space weather societal impacts on the heavily populated North American continent. Millstone Hill coordinates closely with space missions such as NASA’s THEMIS, Van Allen Probes [e.g. Foster et al., 2014], and MMS, and provides fundamental plasma measurements for the emerging cubesat community (e.g. upcoming NASA funded AERO and VISTA missions). The Facility maintains a geomagnetic storm rapid response capability that can trigger full incoherent scatter radar experiments in ~1 hour.
MIT Global Navigation Satellite System (GNSS) Total Electron Content (TEC) data
The enhanced MIT Automated Processing of GPS (MAPGPS) software suite (Rideout and Coster , Vierinen et al. ) provides production-level, routine calculation of global TEC maps directly available in the Madrigal database. Total electron content observations are foundational to many modern scientific studies and are a key method of observing the global ionosphere’s response to normal variations and to geomagnetic storms.
GNSS TEC maps are generally available at a few days behind real time, dependent on global receiver data uploads and processing priorities. These maps are in high demand throughout the scientific community. A significant new GNSS TEC product was developed in 2016, providing the community with an information-rich line of sight measurement alongside the traditional vertically binned TEC maps. There are ~100-200 million line of sight TEC measurements per day, which allow users to calculate a wide variety of highly accurate differential TEC products using the very low point-to-point variance found in the individual line of sight data. These products are ideally suited for ionospheric data assimilation, and greatly facilitate the study of transient phenomena associated with space and terrestrial weather phenomena such as traveling ionospheric disturbances.
Madrigal Geospace Distributed Data System
Millstone Hill has actively pursued the development of the Madrigal distributed data system to address the needs of staff and community scientists. A standard in the upper atmospheric community, Madrigal originated at MIT Haystack in the early 1980s prior to being adopted as the basis for the CEDAR database. In 2012, the main CEDAR database moved to a modernized version of the Madrigal platform hosted by MIT, and annually serves hundreds to thousands of unique users across the space science community. Data from hundreds of individual instruments in the CEDAR Madrigal database total over 27 TB of data with rapid growth each year, and MHGF provides multiply redundant long-term archiving of this data.
Madrigal has been adopted by all Geospace incoherent scatter radars alongside a continually expanding range of additional instruments such as Fabry-Perot interferometers, optical imagers, satellite platforms (e.g., DMSP), and GNSS TEC. Its derived parameter engine allows a wide variety of contextual / ancillary geophysical parameters and community models to automatically appear alongside the instrument providers’ primary measurements. Madrigal maintains multiple application programming interfaces providing access to full data capabilities for software-based data analysis. The open source software model has resulted in many community developed enhancements and improved user interfaces, with on demand data provision in popular formats. Yearly Madrigal tutorials at the international IS radar school and CEDAR meeting disseminate information to the next generation of space scientists on how to use Madrigal data for research.