Posted on 01/13/2005 8:19:16 AM PST by Bones75
Hey all, thought the space lovers out there might like this if they haven't seen it yet. It's the timeline of the Huygens descend noted in Eastern time....
Here is a detailed timeline of major entry events on Jan. 14 (in EST; all times represent when an event occurs relative to signals received on Earth). Explanations for key events from the European Space Agency's Huygens website; Cassini timeline events provided by the Jet Propulsion Laboratory:
Jan. 14
02:33 AM (-02h40m) - Cassini solid state recorders prepped for support 02:45 AM (-02h28m) - Cassini transition to thruster control for relay 02:55 AM (-02h18m) - Cassini: final recorder configuration for relay 02:57 AM (-02h16m) - Turn on Probe receivers 03:09 AM (-02h04m) - Cassini turns toward Titan 03:21 AM (-01h52m) - Turn to Titan complete 03:24 AM (-01h49m) - Cassini disables X-band downlink 04:51 AM (-00h22m) - Probe turns transmitters on (low power mode) 05:13 AM (-00h00m) - Probe reaches the discernible atmosphere: 789 miles 05:16 AM (+00h03m) - Probe feels maximum deceleration
05:17 AM (+00h04m) - Pilot chute: 106-118 miles altitude; Mach 1.5; The parachute deploys when Huygens detects that it has slowed to 895 mph, at about 112 miles above Titan's surface. The pilot parachute is the probe's smallest, only 8.5 feet in diameter. Its sole purpose is to pull off the probe's rear cover, which protected Huygens from the frictional heat of entry. 2.5 seconds after the pilot parachute is deployed, the rear cover is released and the pilot parachute is pulled away. The main parachute, which is 27.2 feet in diameter, unfurls.
05:18 AM (+00h05m) - At about 99 miles above the surface, the front shield is released. Forty-two seconds after the pilot parachute is deployed, inlet ports are opened up for the Gas Chromatograph Mass Spectrometer and Aerosol Collector Pyrolyser instruments, and booms are extended to expose the Huygens Atmospheric Structure Instruments. The Descent Imager/Spectral Radiometer will capture its first panorama, and it will continue capturing images and spectral data throughout the descent. The Surface Science Package will also be switched on, measuring atmospheric properties.
05:32 AM (+00h19m) - Main parachute separates and drogue parachute deploys: The drogue parachute is 9.8 feet in diameter. At this level in the atmosphere, about 78 miles in altitude, the large main parachute would slow Huygens down so much that the batteries would not last for the entire descent to the surface. The drogue parachute will allow it to descend at the right pace to gather the maximum amount of data.
05:49 AM (+00h36m) - Surface proximity sensor activated: Until this point, all of Huygens's actions have been based on clock timers. At a height of 37 miles, it will be able to detect its own altitude using a pair of radar altimeters, which will be able to measure the exact distance to the surface. The probe will constantly monitor its spin rate and altitude and feed this information to the science instruments. All times after this are approximate.
05:56 AM (+00h43m) - Possible icing effects to Probe (31 miles)
06:57 AM (+01h41m) - Gas Chromatograph Mass Spectrometer begins sampling atmosphere: This is the last of Huygens's instruments to be activated fully. The descent is expected to take 137 minutes in total, plus or minus 15 minutes. Throughout its descent, the spacecraft will continue to spin at a rate of between 1 and 20 rotations per minute, allowing the camera and other instruments to see the entire panorama around the descending spacecraft.
07:19 AM (+02h06m) - Cassini closest approach: 37,282 miles flyby at 12,080 mph, 93 deg phase
07:30 AM (+02h17m) - Descent Imager/Spectral Radiometer lamp turned on: Close to the surface, Huygens's camera instrument will turn on a light. The light is particularly important for the 'Spectral Radiometer' part of the instrument to determine the composition of Titan's surface accurately.
07:34 AM (+02h21m) - Surface touchdown: This time may vary by plus or minus 15 minutes depending on how Titan's atmosphere and winds affect Huygens's parachuting descent. Huygens will hit the surface at a speed of 11.2-13.4 mph. Huygens could land on a hard surface of rock or ice or possibly land on an ethane sea. In either case, Huygens's Surface Science Package is designed to capture every piece of information about the surface that can be determined in the three remaining minutes that Huygens is designed to survive after landing.
09:44 AM (+04h31m) - Cassini stops collecting data; Huygens's landing site drops below Titan's horizon as seen by Cassini and the orbiter stops collecting data. Cassini will listen for Huygens's signal as long as there is the slightest possibility that it can be detected. Once Huygens's landing site disappears below the horizon, there's no more chance of signal, and Huygens's work is finished.
09:46 AM (+04h33m) - Cassini probe data partitions write protected 09:54 AM (+04h41m) - Cassini turns toward Earth 09:57 AM (+04h44m) - Turn to Earth complete 10:06 AM (+04h53m) - Critical sequence ends 10:07 AM (+04h54m) - Post-Probe tracking begins (Canberra)
10:14 AM (+05h01m) - First data sent to Earth: Getting data from Cassini to Earth is now routine, but for the Huygens mission, additional safeguards are put in place to make sure that none of Huygens's data are lost. Giant radio antennas around the world will listen for Cassini as the orbiter relays repeated copies of Huygens data.
10:17 AM (+05h04m) - Probe data replay begins (Canberra: 66,360 bps) 12:57 PM (+07h44m) - End playback of first partition 01:04 PM (+07h51m) - Ascending ring-plane crossing: 18.4 Saturn radii 02:00 PM (+08h47m) - Start tracking at Madrid (142,200 bps) 05:07 PM (+11h54m) - End first full playback of all Probe data 08:29 PM (+15h16m) - Full data set on Earth (likely three hours earlier) 10:35 PM (+17h22m) - Start tracking at Goldstone
Jan. 15
07:07 AM (+01d02h) - Power on of orbiter instruments 08:30 AM (+01d03h) - End nominal playback of Probe data
Bones
Cool !
thanks!
Looking forward to watching all this on the Discovery Science Channel.
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