Neutralization tests on the SERT II spacecraft

Development and flight history of SERT 2 spacecraft

“…Neither beam probe filament burned out and spacecraft potentials could be measured through 1991 by using the beam probes. 19 Contamination panel test results. The location of the solar cell contamination panels was poorly chosen.…”

“…24 Extensive probing of an 85-mA beam was done in 1979. 19 The 1979 beam probe results indicated a ±15° beam divergence at 85 mA, but the beam plasma potential was 15 to 20 V lower owing to the lower value of beam current. Figure 20 shows the beam plasma potential of both 250-mA and 85-mA beams.…”

“…With center-tap ground the spacecraft potential was -7 V; it shifted to -29 V with negative solar array ground. 19 For most of the 1970 tests, the thruster solar array was center-tap ground. With the exception of the spacecraft potential shift, no observable effects occurred to solar array performance or life with either grounding position.…”

“…Refer to Ref. 19 for a complete discussion of how cross neutralization was possible with the plasma densities involved. Cross neutralization could be completely controlled by voltage bias of either neutralizer; that is, a positive bias to neutralizer 2 reduced its emissions to zero with all the neutralizing electrons coming from neutralizer 1, and conversely.…”

“…About I km of beam distance would enable thermal dispersion of the ions so that the beam density would be reduced to the ambient density at the SERT II altitude of 1000 km, namely 10 11) ions/m3 . The SERT 11 tests of 1979 19 indicated that space electrons might be drawn into the ion beam any place along its length. The neutralizer on the spacecraft only needed to emit a few milliamperes of electrons into the beam to maintain beam neutrality.…”