The scientists who are directly involved with the mission get first crack at the data. It is an outreach/education decision to release raw images essentially i

The scientists who are directly involved with the mission get first crack at the data. It is an outreach/education decision to release raw images essentially immediately. That decision is made on a mission-by-mission and instrument-by-instrument basis. The mission scientists certainly have near real time processing for most of the correction steps applied, though there may be some fine tuning before the final archival release. The big reason for not sharing the same data publicly is to keep a lock on first publication of scientific results.