Immaculate Constellation
IMMACULATE CONSTELLATION, as described by journalist Michael Shellenberger, is an Unacknowledged Special Access Program (USAP) designed to collect high quality data on UAP. By using the governments equities, a chain of custody can be assured. The high quality nature of the sensor platforms also increase the quality of data collected. This could be visual, electromagnetic, thermal or any number of observables.
Man in the Middle
The program functions similarly to a MITM attack on cyber-information systems. IMMACULATE CONSTELLATION positions itself between the constellation of US intelligence collection assets and the rest of the mil/gov enterprise. By doing so, they get first pick at any data coming over the wires, thus preventing it from ever reaching the rest of the intelligence community.
Classification
Because IMMACULATE CONSTELLATION is an unacknowledged special access program, it can be inferred that materials collected under the auspices of this program is classified TOP SECRET SCI-SAP. In addition to high level vetting required to obtain a TS clearance, the individual being read into the program would need to satisfy any additional requirements specified by the program's security manager as well as have a demonstrated need to know.