The primary purpose of the San Marco-D/L (San Marco 5) Spacecraft was to explore the
relationship between solar activity and thermosphere-ionosphere phenomena. The spacecraft
had a planned lifetime of one year. The science investigations used the following five
flight sensors:
- a Drag Balance Instrument (DBI) for determining neutral density,
- a Wind and Temperature Spectrometer (WATI),
- an Ion Velocity Instrument (IVI),
- an Airglow-Solar Spectrometer (ASSI), and
- an Electric Field Meter (EFI).
The satellite was a 96.5 cm-diameter sphere with four 48 cm canted monopole telemetry
antennas and three orthogonal pairs of electric field probe sensors (one pair oriented
along the spacecraft spin axis). An internal structural cylinder (26 cm diameter) extends
slightly through the sphere and was coincident with the satellite spin axis. The power
supply consisted of a solar-cell array split into two sections, two rechargeable NiCd
batteries, and associated circuitry. The satellite attitude data were provided by a
triaxial magnetometer, a horizon sensor, a digital sun sensor, and a star tracker for
calibration. A magnetic torquing system was used to control spin rate and spacecraft
attitude. The spacecraft reentered on schedule on 6 December 1988. All instruments
operated as planned, except WATI which failed to respond to commands after 20 days (fuse
failure). The spacecraft performed nominally throughout its lifetime. Final data were
acquired at 150 km during re-entry.
The planned cooperative San Marco-D/M spacecraft was
cancelled.
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