The main objective of the thermal control subsystem is to keep the entire satellite and the equipment it houses within the temperature ranges specified for each phase of the mission. In general, two ranges are distinguished: the operational temperature range, which defines the temperature limits within which the instrument can operate; and the survivability range, which defines the maximum and minimum temperatures that the instrument can withstand without being damaged. Thermal monitoring must also ensure that the maximum thermal gradients are below those specified.

Picture of the MLI mounted on the bottom panel of UPM-Sat2.

Thermal control of UPM-Sat 2 is primarily passive. The design is to insulate the satellite from the exterior through the surface finishes of the structure and through MLI, but to allow internally generated heat to be radiated away.
However, there is an active control system for the battery, which is isolated from the rest of the satellite: it is supported on a DELRIN base that insulates it conductively, and is wrapped in a SLI that insulates it radiatively. In addition, heaters powered by two independent circuits, both connected directly to the power line, are attached to the battery base. Thermostats on each line allow the heaters to be switched on and off in such a way that the battery temperature does not drop below 10ºC.
Detail of the battery assembly and its active thermal control system: you can see the heaters and thermostats glued to the underside of the battery tray and the fully assembled battery with the SLI.

Thermal analyses make it possible to verify the behaviour of the satellite and the various on-board instruments under orbital conditions and in different operating modes:

  • Latency mode: When the battery charge drops below the set minimum threshold, the satellite shuts down to let the solar panels charge the battery for 2 hours and 56 minutes. Only the battery thermal control system (Cold Case) operates.
  • Operational mode at maximum power: The satellite is analysed in orbit with the maximum dissipation profile to verify that it does not heat up above the set temperatures (Hot case).


Representation of a temperature distribution of
UPM-Sat 2 during nominal on-orbit operation.
Temperatures are shown in degrees Celsius.


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The University Institute of Microgravity "Ignacio Da Riva" is part of the Universidad Politécnica de Madrid. We have one site at the Escuela Técnica Superior de Ingeniería Aeronáutica y del Espacio, within the Moncloa campus, and another at the Montegacedo campus.

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