The [Mars Odyssey](https://en.wikipedia.org/wiki/2001_Mars_Odyssey) orbiter is currently the [longest-serving spacecraft at Mars](https://mars.nasa.gov/news/8911/nasas-odyssey-orbiter-marks-20-historic-years-of-mapping-mars/). Launched and put into service in 2001, it continues to take infrared pictures and gamma-ray spectra of the Martian surface, and (most importantly) is one of the most active relay satellites for the lander (InSIGHT) and rovers (Curiosity and Perseverance) on the surface.

It's orbit is sun-synchronous and it has solar panels, so theoretically it should continuously get solar power. However, one would expect a battery backup, and 20 years is a long lifetime for most battery technologies. **Does Odyssey have batteries, and what type are they?** Do we know how well they still work?