Power, heat and surface evidence

The Lunokhod design combined solar collection and thermal protection in a hinged lid: its solar panels were exposed during daylight, and the lid closed at night to help conserve heat. The National Research Council describes independently driven wheels and the enclosed instrument housing as parts of the same mobile laboratory.

In an original design exercise, drawing enough electrical power and staying within a usable temperature range are separate requirements. Meeting one does not automatically meet the other. A scientific instrument can receive power yet be outside its operating temperature range; an insulated instrument can stay warm without having enough energy for a measurement.

Suppose an original classroom rover has 10 energy units available after its survival reserve is protected. A drive costs 4 units, an instrument observation costs 3 and returning the data costs 2. The whole sequence costs 9 units and leaves 1. These invented values illustrate accounting; they are not Lunokhod battery capacities or recorded operating costs.

Adding a second 3-unit observation would exceed that budget. A team could shorten the drive, defer a measurement or wait for additional energy if conditions permit. Transmitting data belongs in the plan: an observation that remains inaccessible onboard cannot yet support an analysis on Earth. State the reserve and assumptions before comparing alternatives.

Lunokhod 2 launched with Luna 21 on January 8, 1973, and landed on January 15. NASA’s historical chronology records its departure from the delivery lander on January 16, the end of surface operations on May 10, and the public end-of-mission announcement on June 3. These dates describe different events; a later announcement must not become the landing date.

The accompanying LRO image shows the Luna 21 lander and rover tracks, photographed long after the expedition. Its image date, the landing date and the end of driving answer different questions. In an archive exercise, keep an event’s occurrence separate from when it was photographed, announced or entered into a catalogue.