Delete comment from: Ken Shirriff's blog
Great article, took me back to the beginning of my career working on radar systems as a new degree fresh-out.
In the normal NASA redundant manner, they also had a microwave C-band (4.5GHz) radar system for tracking missile tests, and improved it for use with Apollo at lunar ranges. The design team i joined in 1966 made a mod-kit for our FPQ-6 pulsed radars to add Coherent Signal Processing (CSP) that added Doppler velocity tracking to the radar, with a whole new transmitter. It skin tracked, or tracked a coherent C-band transponder, and did spacecraft acquisition to start the tracking. Tight Doppler frequency control allowed narrow band (Hz) crystal filters at 100KHz-IF to reduce data noise in the 4 axis tracking servo loops (Range, Az, El, Velocity) and the system computer (RCA 4101 http://www.carnarvonspace.com/wiki/index.php?title=RCA_Computer) resolved the Range-rate vice Doppler-velocity ambiguity (Invarient Embedding technique). To acquire the target velocity we used a received I&Q sample time compressor and correlated with ambiguous velocity & acceleration profiles; using p-mos serial shift register memories 16, 32, or 64 words long, with the rest of the DTL logic. The angle tracking loops were integrated in the computer software, while the sigpro hardware tracked the range & Doppler, at 160, 320, or 640 PRF.
We used H/P frequency synthesizers, a big crystal oscillator, and an rf multiplier, for the transmit exciter and receiver local oscillators; stepped the LO synth by one Hz LSBs to track Doppler.
A few years later, we installed a simplified Doppler Velocity Extraction System (DVES) in our FPS-16 and MPS-36 instrumentation test range radars.
I really enjoyed the article about the Unified S-band Tracking and Communication link.
Apr 29, 2022, 5:41:07 PM
Posted to The digital ranging system that measured the distance to the Apollo spacecraft