Orbital properties of the West Ford dipole belt

A passive satellite deorbiting strategy for medium earth orbit using solar radiation pressure and the J2 effect

“…In the 1960s thousands of small metal needles were launched into high altitude polar orbits in a bid to improve long-range HF radio communications. Although some of these needles have meanwhile reentered the atmosphere, large numbers still remain in their orbits as space debris [15]. Figure 2 shows the inclination and altitude of the different space object groups with tracked space debris and rocket bodies shown in light grey in the background.…”

Last of the West Ford Dipoles

“…Since the spread in orbital lifetimes is long, in comparison with 24 hours, the dipoles were distributed almost uniformly along each latitude circle; their density per unit surface area should therefore be greatest in the polar regions. A simple calculation (7) demonstrates that the maximum macroscopic surface density is about 5 dipole/ km2. Search of a sufficiently large area (and depth of snow) to ensure a probability of 0.9 of recovering at least one dipole in the arctic is feasible, but expensive (21).…”

Orbit design for future SpaceChip swarm missions in a planetary atmosphere

“…Hence, the elliptical ring of spacecraft will form wave-like patterns which circulate around the elliptical ring, with peaks in density at the apogee [41]. Considering, for example, the mission in Section 4.2, the carrier spacecraft takes 95 days 8 to cover a vertical line in the eccentricity- phase space (i.e. its orbit apse-line will cover all the possible orientations with respect to the Sun-Earth line), while the decay time of the SpaceChip orbit is between 538 days (for release conditions close to / 0 sc   ) and less than 100 days (for release condition close to / sc   ).…”

“…rather than performing complex analysis on each single device [1]. Moreover, their disposability enables mission designs with high risk, since a lost device can be easily replaced, and the average behaviour of the swarm can be exploited, rather than the evolution of each satellite 5 [4,8,9].…”

“…As an early example of a SpaceChip-scale swarm, project West Ford in 1963 placed a ring of 8 4.8 10  copper dipole antennas (1.78 cm long needles, with a diameter of 17.8 μm) into orbit to allow global radio communication [8]. The motion of the individual dipoles, from dispensing to final re-entry through the atmosphere was both modelled and observed.…”