Power & Thermal Subsystem

The Spacecraft Payload

The spacecraft payload consists of nine science instruments. Fourteen instrument modules, two experiment heaters, and two compensation heaters are connected to the main bus via the Main Switch, and seven additional payload heaters are connected to the Main Bus via fuses.

The Main Switch is essentially a circuit breaker that protects the Main Bus and spacecraft power subsystems from electrical faults that may develop in the payload. The Main Switch Overcurrent Detector will open the Main Switch if there is an unexpected surge in the current on the payload bus. Fortunately this very rarely happens, as it takes 2-3 days to recover from such an event and to reconfigure the instruments to the desired state. The Main Switch opening automatically is termed Disconnect Non-Essential Loads (DNEL) and can also be caused by faults other than overcurrent detection on the payload bus.

The following items are connected via the Main Switch:


  • The BAM Ion and Electron instruments (SWOOPS).
  • The Interplanetray Dust Instrument (DUST).
  • Fluxgate Magnetometer converters and electronics (FGM).
  • Vector Helium Magnetometer electronics (VHM).
  • Gamma Ray Burst instrument (GRB).
  • Energetic Particle Composition instrument and Interstellar Neutral Gas instrument (EPAC and GAS).
  • Power converters for the COSPIN instruments.
  • Power converters for the Unified Radio and Plasma instrument (URAP).
  • A 0.4W heater for the DUST instrument sensor electronics.
  • A 0.9W heater for the URAP instrument's search coil.
  • The HI-SCALE and its compensation heater.
  • The Solar Wind Ion Composition Spectrometer (SWICS) and its compensation heater.

The following items are fused and connected to the Main Bus:


  • The SWICS 2.0W 'Bakeout' heater.
  • A 0.8W heater for the DUST instrument sensor electronics.
  • A 1.1W thermostatic heater for the Vector Helium Magnetometer.
  • A 2.2W heater for the Gamma Ray Burst instrument.
  • Heaters with a total power of 6W for the HI-SCALE.
  • A 0.5W heater for the EPAC.
  • A 1.8W heater for COSPIN High Energy Telescope.

Note that each element of Ulysses' payload is a very complex instrument; this page only deals with the payload's impact on the spacecraft power subsystem. For descriptions of an instrument's design and operation, please see the instrument Home Pages by clicking on the instrument names.


For the power consumption breakdown of the payload, see the Current Power Budget