Spirit, and MER 2 team, you were amazing. Thank you for the excitement, the science, and most of all, the inspiration.
Some of you will remember that I followed, and blogged quite a bit about, the Mars Exploration Rover missions back in early 2004. Here's a quick look back at Spirit's EDL from my blog archives:
Some timeline info that I think I've got right (please let me know in the comments if you've got better info). Times are PST:
6:45 - NASA TV begins Mars Exploration Rover coverage.
8:29 - Spirit enters martian atmosphere at about 12,000 mph.
8:33 - Spirit has slowed to about 1,000 mph.
8:34:40 - Parachute opens at an altitude of about 30,000 feet, and Spirit slows to about 200 mph.
8:34:54 - Airbags inflate, retro rockets fire, the spacecraft slows to a hover at about 60 feet from the surface, and spirt drops to surface.
8:35 - Spirit Touchdown.
(about) 8:45 - Radio signals from Spirit begin to arrive at Earth and we start to get the reports that Spirit will have broadcast about every 10 seconds of the descent.
From the broadcast:
Wayne Lee, a mission planner for Pathfinder, MGS and MER interviewed.
None of the possible 3 trajectory corrective maneuvers that could have been made in the last couple of days were necessary. The craft is "perfectly on target".
The project team will be listening for transmissions directly from Spirit and from MGS. Spirit will be broadcasting signals (tones) directly back to Earth as well as to the Mars Global Surveyor which can forward that on to us.
The turn to entry, a maneuver to orient the craft with heat shields facing forward, has begun. The antenna is pointed toward the Earth during the trip to Mars but when the turn to entry phase begins, the antenna start to point away from us so the signal strength decreases. The project team has measured the beginning of this signal weakening indicating that the maneuver has begun. It should complete in about 10 minutes (7:21).
The heaters that will bring up to temperature the propellant for the rocket boosters which inflate the airbags have activated. Canberra tracking stations are locked in at 10 bits/sec.
Correction from previous post: Turn to entry won't be finished until 7:27.
When turn to entry completes, we will be about one hour from contact with the Mars atmosphere.
The maneuver should be complete. 1 hour 6 minutes from hitting the top of the Martian atmosphere.
Next major event in roughly half an hour is the venting of coolant which isn't needed for the surface mission.
Additional commentary from Rob Manning, EDL lead:
Minor adjustments have been made in the last couple of days to account for atmospheric temperature changes from dust storms. Enabled pyro switches a bit earlier than planned. Several improvements have been made since Pathfinder. We have a descent camera and small rockets in the backshell to help stabilize the descent if necessary. This descent is all automatic. No intervention from Earth.
54 minutes to atmospheric entry.
Wayne Lee says that at 7:47 polling of subsystems will happen to confirm that turn to entry has completed.
Additional info from Steve Squyres, the principal investigator for the Mars Exploration Rovers' science packages: It will probably be about a week and a half before the rover rolls into action. Between landing and then, we'll be "taking a look around" with the rover cameras and picking target rocks. The cameras on this vehicle are 3.5 times the resolution of previous surface pictures, giving the rover much better "eyesight" to pick our targets and drive directions.
Each of the EDL substations (hull protection, flight software, power, flight ACE, telecom, comm, MGS, MGS MOC, Odyssey, nav, mdot, and a couple others that I missed) have reported in and everything sounds good except for a minor incident with the Gas Generator heaters. The heaters are rising in temp slightly faster than expected and will be at 5 degrees Celsius rather than the desired ?
Global Surveyor, including the MOC, as well as the Odyssey satellite are online and in position to track Spirit EDL.
Telemetry indicates that the coolant has been vented into space. During this venting the craft wobbles slightly. Tiny rockets fire to do a "clean-up" which should be complete in about 20 minutes.
More info from Pete Theisinger: 40% chance of hearing the landing tones tonight. Depending on how easily the airbags get pulled in and the petals open, it will talk to Odyssey tonight about 10:30. Then tomorrow at 8am with MGS, then noon at Odyssey then afternoon with sunrise (and earthrise) it can try to talk directly to us again.
Next major event is separation of the cruise stage flight package.
Cruise stage separation at 8:13 - (confirmed).
Vehicle pointed 1.2 degrees from desired attitude (could be off by 10 degrees and be OK so this is good).
Venting of coolant has occurred confirmed by pressure telemetry.
Airbag engineers reported that the temp situation isn't going to be an issue :D
Another sub-station report in progress.
As expected, Spirit jettisoned the cruise stage, and along with it the communication link that we've had with the craft for its journey thus far. Communication with the lander has been re-established. Lander 12 minutes from entry.
The Cruise stage has likely burned up. Applause and thanks to the cruise stage and the cruise stage team.
Spacecraft has not yet begun to decelerate.
Sub-station polling in progress.
All substation reports are reporting ready for EDL. Everything's "green". We are 3.5 minutes away from hitting the top of the Martian atmosphere. We are 11 minutes and change from landing.
Once Spirit has entered the atmosphere, the craft won't be transmitting its detailed telemetry but will broadcast a series of semaphores/tones which indicate the success of the various stages of descent.
Atmospheric entry has begun. 73 miles altitude 12,192 mph.
Atmospheric deceleration has begun (nav team reporting).
1 minute after entry vehicle is at 46 miles altitude. 12,175 mph.
Peak Heating upwards of 1600 degrees Celsius.
Tones coming in. Decelerating at 5.9 Gs.
2:21 seconds after entry. 16 miles altitude. 4,000 mph.
Deceleration at 2.4 Gs. Parachute deployment in 60 seconds.
Wobbling increasing. 3:35 after atmospheric entry. 45,000 feet altitude. 1.1 Gs deceleration.
Parachute deployment should have jut occurred at 25,000 feet.
Parachute detected. Craft is subsonic.
Heat shield jettisoned. (applause).
Craft should be on the ground.
Any signal from here out indicates that the craft is on the ground alive.
"We are bouncing on the surface of Mars. This is a very good sign!"
No signal now :|
Bouncing and rolling could continue for 10 minutes.
Vehicle could bounce and roll for another 7 minutes. Still no signal.
Some indication of receipt of enough data at Mars Global Surveyor from MER to suggest that MGS got data after Spirit touchdown. We'll receive the actual data from MGS in about 4 minutes.
Update: MGS was receiving data from MER during the descent. Initial indications are that MGS has enough data (greater than 250 KB) which might be indicative of reception of data after landing.
We have a solid signal from Spirit. "This is beautiful". Things look good. Base panel is down so the craft won't have to flip itself to open. Airbag retraction should be underway. News briefing in 30 minutes.
I'll keep an eye on things and post more as it comes in but that's the end of my dedicated full-time reporting ;-) on the MER EDL. Hope you enjoyed it :D
You can read these posts and many many more (about 300,000 words worth) in my archives.