A NASA spacecraft called the Lunar Reconnaissance Orbiter (LRO) has been circling and studying the Moon since June 2009. On-board is a shoebox-sized instrument called CRaTER (Cosmic Ray Telescope for the Effects of Radiation). It detects some of the smallest and fastest particles in the universe.

CRaTER's goal is to help scientists study the radiation from cosmic rays and how it will affect astronauts. Scientists also use CRaTER to discover how cosmic rays affect the Moon. (Remember: CRaTER doesn't study the Moon's craters. It studies cosmic rays!)

"Hi! I'm Ray, the cosmic ray. I'll be helping you to learn about CRaTER and LRO. You can start by exploring one of the sections above."

This website has four main sections:
The Mission section describes both LRO and CRaTER: what they are and how they got to the Moon.

The Science section explains the science done with CRaTER.

The Engineering section describes how CRaTER was built and tested and how scientists receive its data.

The Future section contains links to NASA websites describing how humans will continue to explore space.

Educator Resources contains a collection of websites, videos, and documents to learn more about LRO, cosmic rays, and the Moon.