In case someone else had similar thoughts, sharing my back of an envelope assessment. Cm-244 has long been studied as a fuel source for both as RTG & RHU(https://osti.gov/servlets/purl/4485122). APXS used in pragyan( https://arxiv.org/pdf/1910.09232) has an operating temperature is -35C. The excess heat is radiate into the metallic body of the rover (along with peltier for active cooling). Seems the APXS has 6 source of 8mm 0.6mm Cm-244 each. Cm-244 has a density of 11.7g/cm3 . That comes ~0.1587g. Is it enough to heat? Cm244 has a half life of ~18years, generates heat of 315w per 31.9g from a metric ton of fuel after 1 year. So I guess the generated heat will be punny. Lol. Apparently Change-3(https://www.sciencedirect.com/science/article/am/pii/S0275106216300595) had an APXS is of similar design with a Pu based for 4W RHU just to heat the APXS. Seems this APXS design seems to have been used since the days of Sojourner. Staying on the theme of payloads, the SHAPE payload on the "non-orbiter" orbiter has a potential of being highly cited, it could end up being something similar to how standard candle is used in astronomy.