The Oldest Television and Calibration Satellites Still in Use: An Overview
Television satellites play a crucial role in modern communication, enabling television and radio broadcasts from a stationary position in space. These satellites need to be geostationary to maintain their position relative to the Earth's surface, but they also require regular station-keeping adjustments to stay in orbit. Propellant for these adjustments is limited, which eventually leads to the satellite's end of life. However, there are also older satellites in orbit that continue to serve specialized purposes, such as calibrating ground-based radars and studying atmospheric effects.
The Oldest Geostationary Television Satellites
While some geostationary television satellites have reached the end of their operational life and are no longer used for regular broadcasting, others continue to be useful for specialized tasks. Several satellites are often utilized for Satellite News Gathering (SNG), where a mobile truck transmits terrestrial news back to the studio via satellite. These satellites can be fine-tuned in real-time to maintain optimal performance, even as they move in orbit.
The Legacy of Calsphere/Dragspheres (1964)
A fascinating case study of old satellites still in orbit are the Calsphere/Dragspheres, two passive satellites launched in 1964. These satellites were designed to measure the effects of atmospheric drag on their orbits and to calibrate ground-based radars. They were small and unpowered and served as important references for atmospheric drag studies.
Technical Details of Calsphere Satellites
There were two Calsphere satellites launched in 1964:
Calsphere 1 FIRST CalsphereCalsphere 1 was launched on October 6, 1964, with a mass of only 0.9 kg. Its orbit parameters are as follows:
Perigee: 976.9 km Apogee: 1018.1 km Inclination: 90.1° Period: 104.9 minutesSimilarly, FIRST Calsphere (Calsphere 2) was launched on May 6, 1965, with a mass of 9.5 kg:
Apogee: 2795 km (1736 mi) Perigee: 2786 km (1731 mi) Inclination: 32.1° Period: 145.60 minutesAfter 30 years, the orbit of the more massive satellite (Calsphere 2) remained nearly unchanged, while the lighter satellite (Calsphere 1) experienced a 50 km drop in altitude.
Lincoln Calibration Sphere (1965)
Another well-known calibration satellite is the Lincoln Calibration Sphere (LCS), which was first launched in May 1965. This satellite is a hollow metal sphere with a precise radar cross-section, making it ideal for radar calibration. It has been in orbit for several decades and continues to serve its primary purpose.
Technical Details of Lincoln Calibration Sphere
The key technical details for the Lincoln Calibration Sphere are as follows:
Launch Date: May 6, 1965 Apogee: 2795 km (1736 mi) Perigee: 2786 km (1731 mi) Inclination: 32.1° Period: 145.60 minutesConclusion: Evolution of Satellite Technology
The longevity and varied functions of these older satellites highlight the advancements in satellite technology. While newer satellites are continuously developed and launched, the legacy of older satellites like the Calsphere and LCS remains significant. These satellites continue to contribute valuable data and provide invaluable references for ongoing research and development in aerospace and radar technology.