The events on this day in history for our heritage companies are noted below:
The earliest event was in 1955, the latest event was in 2021
No milestone events (5 to 65+ years ago)
Human Spaceflight:
2021 – LM Orion spacecraft for Artemis I completed and turned over to NASA (latest iteration)
Military and Classified Programs:
1967 – LAUNCH: Classified mission, Thor SLV-2A/Lockheed Agena D, SLC3W, VAFB
1970 – LAUNCH: Classified mission, MM Titan 23B, SLC4W, VAFB
Exploration and Interplanetary Programs:
2005 – ESA Huygens probe lands on the Saturn moon of Titan (Cassini/Huygens launched by LM Titan IVB/Centaur in 1997)
Earth-Monitoring and Civil Weather Satellite Programs:
NONE
Commercial Programs:
1996 – LAUNCH: LM Koreasat2, Delta 7925, LC17B, CCAFS
Test, ICBM, FBM programs:
1955 – Contract awarded to Aerojet-General for Martin Titan I ICBM engines
1961 – LAUNCH FAILURE: Lockheed Polaris A1, SSBN-601, ETR
1965 – LAUNCH: MM Titan I launch, 395-3A, VAFB
Other:
NONE
The photos today include a diagram of Huygens and images taken during descent at landing of the ESA Huygens probe on the Saturn moon of Titan in 2005. Huygens had several experiments on-board to measure winds and atmospheric properties during descent and on the surface. The probe’s transmissions lasted about 90 minutes after touchdown due to battery constraints. The temperature at the landing site was 93.8 Kelvin (-179.3 °C; −290.8 °F) and pressure was 1,467.6 mbar (1.4484 atm), implying a methane abundance of 5 ± 1% and methane relative humidity of 50% near the surface.
Cassini/Huygens had an interesting data relay design flaw that was detected after the launch in 1997. Here’s the story, taken from Wikipedia:
Since Huygens was too small to transmit directly to Earth, it was designed to transmit the telemetry data obtained while descending through Titan’s atmosphere by radio to Cassini, which would in turn relay it to Earth using its large 4 m (13 ft) diameter main antenna. Some engineers felt uneasy about the fact that, in their opinion, this feature had not been tested before launch under sufficiently realistic conditions. They managed, with some difficulty, to persuade superiors to perform additional tests while Cassini was in flight. In early 2000, simulated telemetry data was sent at varying power and Doppler Shift levels from Earth to Cassini. It turned out that Cassini was unable to relay the data correctly.
This was because under the original flight plan, when Huygens was to descend to Titan, it would have accelerated relative to Cassini, causing the Doppler Shift of its signal to vary. Consequently, the hardware of Cassini’s receiver was designed to be able to receive over a range of shifted frequencies. However, the firmware failed to take into account that the Doppler shift would have changed not only the carrier frequency, but also the timing of the payload bits coded by phase-shift keying at 8192 bits per second.
Reprogramming the firmware was impossible, and as a solution the trajectory had to be changed. Huygens detached a month later than originally planned (December 2004 instead of November) and approached Titan in such a way that its transmissions travelled perpendicular to its direction of motion relative to Cassini, greatly reducing the Doppler shift. This was successful.
