This week in SF history— January 31, 1961: Mercury MR-2 (wikipedia.org)Spaceflight news— Starship Hopper's nose cone knocked over by heavy winds. (brownsvilleherald.com)Short & Sweet— Commercial crew swaps an astronaut. (spacenews.com)— Blue Origin is coming to Alabama. (spacenews.com)— Hubble’s primary camera is back online.(spaceflightnow.com)Questions, comments, corrections— By-line mixup, Chris Bush vs Ben McPheronData Relay: Spacecraft Navigation— Thanks to Ben McPheron for researching and presenting this topic — twitter.com/bdmcpheron — benjaminmcpheron.com — youtube.com/DMExplains— Three interrelated systems: Guidance, Navigation and Control (GNC) (wikipedia.org)— Onboard sensors — Even high quality sensors drift (PDF: orbit.dtu.dk) (youtube.com) —Inertial sensors (IEEE) — Gyroscopes (PDF: orbit.dtu.dk) — Hubble used gas bearings (spacetelescope.org) — Optical gyroscope (PDF: orbit.dtu.dk) (wikipedia.org) (PDF: nasa.gov) — First optical gyroscope in space was the Rossi X-Ray timing Explorer spacecraft, launched in 1995 (PDF: nasa.gov) — Sagnac Effect (youtube.com) — Inertial measurement Units (wikipedia.org) (nasa.gov) — Magnetometers measure the size and orientation of the magnetic field (PDF: orbit.dtu.dk) — Eight different types in one particular source (engineersgarage.com) — Orbital models (PDF: orbit.dtu.dk)— Non inertial sensors for determining attitude — Sun sensors (PDF: orbit.dtu.dk) (wikipedia.org) — Solar Panels (youtube.com) — Star Trackers/Star imagers (nasa.gov) (PDF: orbit.dtu.dk) (science.gov) — Update rate on star trackers are generally 1-10 Hz, but can be up to 100 Hz at max (PDF: OSApublishing.org) — Hubble’s Fine Guidance System (HubbleSite.org) — Apollo ‘Person In Loop’ Star Tracking (NASA.gov) (Astronomy.com) (youtube.com) — Lovell had to work hard due to the field of debris around his vehicle (wikipedia.org) — Shuttle had one too, located forward and left of commander’s window (NASA.gov) — RADAR/LIDAR (NASA.gov) — Used in Apollo, specifically for lunar landing (NASA.gov)— Offboard sensors — RF beacons can be used as reference (PDF: orbit.dtu.dk) (wikipedia.org) — DSN Precise One Way Metric Tracking (PDF: jpl.nasa.gov) — Single-sample accuracy up to 0.05 mm/s and 3 m (scientificamerican.com) (PDF: researchgate.net) — NASA would like to update this to use laser communications (PDF: nasa.gov) — JPL leading development of a deep space atomic clock to further improve this system (jpl.nasa.gov)Future technologies — X-ray pulsar navigation — Developed at NASA Goddard (PDF: nasa.gov) — Closely analogous to GPS tracking (nasa.gov) — Make use of a large number of extremely stable millisecond pulsars (howstuffworks.com, nasa.gov) — SEXTANT experiment on ISS (nasa.gov)