According to JDIC, both mean "observation". Judging from the Kanji used, I'm guessing the difference is 観測 has a nuance of observing something and measuring some aspect of it or taking data, whereas 観察 is just to observe and monitor what's happening.
Japanese Language Stack Exchange is a question and answer site for students, teachers, and linguists wanting to discuss the finer points of the Japanese language. It's 100% free, no registration required.
Here's how it works:
- Anybody can ask a question
- Anybody can answer
- The best answers are voted up and rise to the top
You guess is right. And 観測 can also mean prediction based on the data observed (e.g. 希望的観測).