A metal plate in LEO will cycle from –170°C to 123°C depending on its Sun face and its time in sunlight. If your picosatellite is spinning, this will even out the heat distribution a bit, but that’s the range to assume. An orbit has approximately half its time in sunlight and the other half in Earth shade, so the temperature behavior is worth modeling.

Since the picosatellite is spinning, this range is fortunately smaller (as heat has time to distribute and dissipate), and with a 90-minute orbit, you should cycle through three ranges: too cold to register; transition regions where the sensor returns valid, slowly changing data; and possibly oversaturating at the high end. You can add a heater if necessary—satellites have used heaters and coolers depending on the instrument and facing.