Several different ground based facilities support the TERRIERS mission by providing coordinated observations and by monitoring the TERRIERS satellite beacon during radio tomography experiments.
The primary science radio beacon receivers will be supplied by the University of Illinois at Urbana-Champaign and by Phillips Laboratory. UIUC has purchased 6 JMR-1a TRANSIT receivers for use with satellite radio beacons. The JMR-1a receivers will be modified for use with the TERRIERS beacon at UIUC. Phillips Laboratory has contracted with NorthWest Research Associates to construct 5 beacon receivers. Phillips Laboratory has agreed to provide these receivers for use in our ground-station chain. We have been in contact with scientists in Taiwan, Japan, Europe, and Russia who have beacon receiver and tomographic reconstruction capabilities. They have verbally expressed interest in providing receiving systems for the support of the TERRIERS satellite program. The receivers use phase-locked-loops to track the beacon transmissions. The effective loop bandwidth is less than 10 Hz.
The polarization of the ground based beacon receiver antennas must be compatible with the polarization of the TERRIERS transmissions. Both circularly polarized and linearly polarized antennas can be used to receive the beacon signals. If circularly polarized antennas are used, 3 dB signal strength is lost but the orientation of the antenna is not critical. Linearly polarized antennas should be aligned with the polarization of the transmissions from the satellite. With the proposed satellite orbit, horizontal polarization will provide optimum reception for ground receiver antennas. Satellite to ground link calculations for a range of 1000 km indicate that a 20 dB signal-to-noise margin will be achieved for a receiver antenna with 10 dB gain and a receiver bandwidth of 10 Hz.
MIT Millstone Hill Radar
The TERRIERS program includes incoherent scatter measurements of the ambient plasma parameters both for technique calibration and campaign operations. During regular satellite overflights, the radar will use elevation scans aligned with the ionospheric projection of the orbital plane to provide a direct measurement of the plasma density altitude profile and its spatial structure. Nominal spatial resolution will be of 30-40 km in altitude and 0.5-10 degrees in latitude. Time resolution for a complete N-S elevation scan covering 20-30 degree of latitude and altitudes from 100 km to 750 km with 30 km altitude resolution and 1 degree latitude resolution is approximately 15 minutes.(this is the repeat cycle time for a scanning experiment). Absolute accuracy depends on varying factors, like external noise background and absolute ionospheric density. There are many factors (such as the fact that a sample is smeared over the pulse length in the ionosphere and the measurement is an average of the regions (e.g. altitudes) covered). The statistical accuracy of a density measurement is better than 5% and total electron content (TEC) should be determined to better than 10%.
Absolute density accuracy is calibrated by comparing the relative measurements made by the radar with "absolute", co-located measurements made with a digisonde. A more-detailed diagnostic program will be run in support of the campaign operations, as required. A total of 40 hours of radar operations are budgeted in order to allow for experiment check-out, calibration, and campaign operations.
As part of the TERRIERS program, a coordinated groundbased-spacebased series of campaigns will be organized to both test and verify techniques, to do in-flight calibration of TERRIERS instruments, as well as to address merged science objectives. Two types of campaigns are planned.
To conduct the Sub-auroral campaign, BU's new CEDAR Optical Tomographic Imaging Facility (COTIF), will be available to support TERRIERS at no cost to the program. Built into this NSF demonstration project is campaign mode support of precisely the type required here. A separate all-sky imager at Goose Bay, Labrador, is also fully operational, supported by ONR to conduct observations and data analysis, and will continue to be operational during the TERRIERS mission.
The Equatorial aeronomy campaign, one that must be scheduled during Equatorial Spread-F (ESF) season at a given site, requires logistic and personnel support. For the Brazilian sector, ESF periods occur from September to March, and thus, for a launch in late 1998, the period February - April 1999 is carried in our baseline plan for the mission. The COTIF instruments, two imaging spectrographs flanking a centrally located all-sky imager, would be set up along an approximately East West magnetic line. This would allow us to reconstruct the cross sections of north-south aligned airglow depletions that define the footprints of depleted fluxtubes/ESF plumes. We have in place a long term cooperative agreement between BU and Brazil's National Institute for Space Physics (INPE) to operate an imager at their observatory in Cachoiera Paulista under the direction of Dr. Y. Sahai. Dr. Sahai has agreed to operate this system during the TERRIERS campaign, and to assist us in locating suitable sites for the COTIF instruments.