BY JUSTIN RAY
Follow the Cassini spacecraft's arrival at Saturn! Reload this page for the latest on the mission.
FRIDAY, JULY 2, 2004
Just two days after the Cassini spacecraft entered Saturn orbit, preliminary science results are already beginning to show a complex and fascinating planetary system. One early result intriguing scientists concerns Saturn's Cassini Division, the large gap between the A and B rings. Read our full story.
Additional coverage for subscribers:
WATCH FRIDAY'S SCIENCE NEWS CONFERENCE QT
THURSDAY, JULY 1, 2004
Making gravity visible, close-up images of Saturn's rings shot by NASA's newly arrived Cassini probe revealed an intricate, never-before-seen tapestry of icy particles herded into spiralling density waves by the effects of nearby moons. Read our full story.
Additional coverage for subscribers:
THURSDAY'S NEWS BRIEFING ON CASSINI'S FIRST PICTURES QT
RING PICTURES ARE PRESENTED WITH EXPERT NARRATION QT
CASSINI RE-DISCOVERS TINY MOONS ATLAS AND PAN QT
CASSINI BOOMING SOUNDS FROM BOW-SHOCK CROSSING QT
CASSINI BEGINS ENGINE FIRING TO ENTER ORBIT QT
BURN ENDS SUCCESSFULLY TO PUT CASSINI IN ORBIT QT
POST-ARRIVAL NEWS CONFERENCE QT
3-MINUTE PREVIEW OF CASSINI'S MISSION QT
CASSINI'S ARRIVAL AT SATURN IS MAKE-OR-BREAK MOMENT QT
AN INTERVIEW WITH THE CASSINI MISSION PLANNER QT
WEDNESDAY'S 12 P.M. EDT CASSINI STATUS BRIEFING QT
A LOOK AT INTERNATIONAL COOPERATION QT
'RING-SIDE CHAT' ABOUT SPACE EXPLORATION QT
AN OVERVIEW OF CASSINI'S RADIO SCIENCE QT
TUESDAY'S CASSINI MISSION OVERVIEW BRIEFING QT
CASSINI'S ARRIVAL AT SATURN EXPLAINED QT
SCIENCE OBJECTIVES FOR CASSINI ORBITER QT
HUYGENS LANDER SCIENCE OBJECTIVES QT
1706 GMT (1:06 p.m. EDT)
A news conference on Cassini's status and the ring pictures beamed to Earth this morning is currently underway at JPL.
The Cassini spacecraft is operating perfectly, says Robert Mitchell, Cassini program manager. A poll of the onboard systems and subsystems shows not a single alarm or glitch occurred last night.
Also, controllers have spent additional time performing tracking of the probe to determine the exact orbit achieved around Saturn. Mitchell says the orbit is right on the target. A scheduled engine firing this weekend that would tweak the orbit may be cancelled due to last night's successful orbit insertion.
1350 GMT (9:50 a.m. EDT)
The first batch of photographs snapped by the Cassini Saturn orbiter earlier today reached the Jet Propulsion Laboratory around 8:30 a.m. EDT, zoomed-in shots of the planet's myriad rings showing a ghostly tapestry of icy, back-lit particles arrayed in sharply defined bands. Read our full story.
1320 GMT (9:20 a.m. EDT)
More pictures are continuing to be received. NASA expected over 40 images in total. They will be posted on the Internet for the public to download later today.
1300 GMT (9:00 a.m. EDT)
Here is an example of Cassini's images that are still flowing into mission control. The pictures are raw and unprocessed.
1245 GMT (8:45 a.m. EDT)
The images being received are black and white, showing the rings in fine detail.
1231 GMT (8:31 a.m. EDT)
The first images taken by Cassini after the entering Saturn orbit last night are beginning to stream into mission control at NASA's Jet Propulsion Laboratory. These pictures were taken as the spacecraft soared over the rings at a close distance never to be repeated during Cassini's four-year tour of the Saturn system.
0718 GMT (3:18 a.m. EDT)
Cassini has reestablished communications with Earth following its science observation period and passage through the ring plane on a descending path. Controllers were anxiously awaiting word from the spacecraft that it has survived this second trek through the ring plane. An ascending passage occurred prior to the engine firing.
The spacecraft is beginning a planned playback of engineering data that was collected and stored onboard during the Saturn orbit insertion burn.
The first pictures taken after the engine burn, which should show the planet's rings in amazing detail, will be transmitted to Earth around 1239 GMT (8:39 a.m. EDT), according to the schedule.
NASA plans a news conference at 1700 GMT (1 p.m. EDT) today for scientists to discuss the images.
After a long day that included Cassini's historic arrival at the ringed planet and a five-and-a-half-hour spacewalk by the International Space Station crew, we now conclude our live play-by-play reports on Cassini.
Check back in a few hours for Cassini's first pictures while orbiting Saturn.
0700 GMT (3:00 a.m. EDT)
Controllers should be reacquiring signal from Cassini around this time.
In a few minutes, Cassini is scheduled to reopen the protective cover over its main engine nozzles. That cover was closed to shield the primary and backup engine during the descending ring plane crossing.
Then at 1049 GMT (6:49 a.m. EDT), the craft is expected to switch to its reaction wheel assemblies for controlling its orientation. Cassini has been using its thrusters for attitude control since before the orbit insertion Wednesday evening.
0610 GMT (2:10 a.m. EDT)
Our post-arrival story has been updated to include quotes from the news conference. You can read the story here.
0517 GMT (1:17 a.m. EDT)
In the news conference underway at JPL, officials report the spacecraft's orbit is right as intended. A small trim maneuver to tweak the orbit is scheduled in a couple of days. Also, the data now indicates the burn ended about a minute early due to the good performance from Cassini's engine.
The spacecraft is doing its first science activities in Saturn orbit. It will pass through the ring plane on a descending track at 0558 GMT.
Communications are expected to be restored at 0700 GMT. That is when Cassini will begin playing data stored onboard from the orbit insertion burn.
0438 GMT (12:38 a.m. EDT)
Cassini successfully arrives at Saturn
NASA's $3.3 billion Cassini probe completed a seven-year, 2.2-billion mile voyage tonight, firing its main engine for a nerve-wracking 96 minutes to successfully brake into orbit around the ringed planet Saturn. Read our full story.
0435 GMT (12:35 a.m. EDT)
A post-orbit insertion burn news conference is coming up at 0500 GMT from the Jet Propulsion Laboratory.
0432 GMT (12:32 a.m. EDT)
Cassini will now reorient itself to begin science observations, snapping close-up pictures of Saturn's rings and probing the magnetosphere. These first images are expected to be received on Earth in about eight hours.
0430 GMT (12:30 a.m. EDT)
Cassini has just phoned home via its main communications antenna, confirming to controllers that the spacecraft is operating normally following the Saturn orbit insertion burn! Controllers are cheering the news!
0428 GMT (12:28 a.m. EDT)
Altitude is now 16,000 miles, velocity is 66,000 mph.
0426 GMT (12:26 a.m. EDT)
This upcoming "call home signal" via the High-Gain Antenna will last only a minute or so. Then Cassini will turn itself to begin science observations.
0424 GMT (12:24 a.m. EDT)
Cassini is passing behind the D ring as seen from Earth. However, this ring should not hamper communications.
0423 GMT (12:23 a.m. EDT)
Cassini is now pointed to Earth on its Low-Gain Antenna, mission control says. A switch to the High-Gain Antenna for communications is expected at 0430 GMT.
0422 GMT (12:22 a.m. EDT)
Cassini is now 15,000 miles above Saturn's cloud tops, traveling at 67,000 mph.
0421 GMT (12:21 a.m. EDT)
Based upon the timeline, Cassini should be completing right now its "critical sequence" of activities for the orbit insertion burn.
0418 GMT (12:18 a.m. EDT)
The spacecraft should now begin turning itself to point toward Earth. A brief High-Gain Antenna communications session is expected in about 12 minutes. This "call home signal" from Cassini will confirm the probe completed the engine firing without going into a safe-mode due to some kind of onboard problem.
0417 GMT (12:17 a.m. EDT)
The Doppler signal indicates the burn went well and the spacecraft has entered a good orbit.
0415 GMT (12:15 a.m. EDT)
"Welcome to Saturn orbit!" mission control says.
0415 GMT (12:15 a.m. EDT)
At this time, Cassini is scheduled to close the protective cover over its main engine nozzles for the upcoming descending pass through the ring plane.
0413 GMT (12:13 a.m. EDT)
Controllers report the burn duration was within one-second of the prediction.
0412 GMT (12:12 a.m. EDT)
MAIN ENGINE CUTOFF! Cassini has completed its braking maneuver as the spacecraft becomes the first man-made object to orbit the planet Saturn!
0410 GMT (12:10 a.m. EDT)
About two minutes are remaining in the scheduled engine burn time. However, the firing time can vary slightly depending on engine performance.
0409 GMT (12:09 a.m. EDT)
Altitude is 12,900 miles as Cassini begins to move past the planet after closest approach. The speed has slowed to just over 68,000 mph.
0407 GMT (12:07 a.m. EDT)
The Doppler signal from Cassini is showing the spacecraft is braking a bit quicker than expected. An over-performance of the main engine during the burn is not a problem.
0405 GMT (12:05 a.m. EDT)
Cassini has emerged from behind the B ring, restoring communications with Earth. The craft is now behind the C ring, but that ring has much less material density than the B ring.
0403 GMT (12:03 a.m. EDT)
Cassini is making its closest approach to Saturn at an altitude of 12,800 miles above the planet's cloud tops. The spacecraft will never again get this close to the planet during its four-year tour of the Saturn system.
0402 GMT (12:02 a.m. EDT)
Ten minutes to go!
0357 GMT (11:57 p.m. EDT Wed.)
Cassini is now 13,000 miles above Saturn, nearing its closest approach. The speed is now 69,000 mph.
0355 GMT (11:55 p.m. EDT Wed.)
With the engine firing accomplished so far, the Cassini spacecraft has been captured into orbit around Saturn. However, this initial orbit is not usable for the probe's science mission. So the engine burn will continue until 0412 GMT to place Cassini into the desired orbit.
0352 GMT (11:52 p.m. EDT Wed.)
Twenty minutes are remaining in Cassini's engine burn.
0347 GMT (11:47 p.m. EDT Wed.)
Cassini's communications outage behind B ring has been occurring for 10 minutes. Controllers predict this will continue for another 18 minutes before Earth will again hear a signal from the spacecraft.
0342 GMT (11:42 p.m. EDT Wed.)
Cassini has 30 more minutes of rocket firing time to complete its orbit insertion. The spacecraft remains out of communication with Earth due to the blockage created by Saturn's B ring. The rings are lettered in the order in which they were discovered.
0338 GMT (11:38 p.m. EDT Wed.)
The spacecraft altitude is now 16,700 miles and the velocity has increased to 66,500 mph.
0337 GMT (11:37 p.m. EDT Wed.)
The material in Saturn's B ring is now blocking Cassini's communications path to Earth. Controllers expect to regain a communications signal from the spacecraft in about 28 minutes.
0336 GMT (11:36 p.m. EDT Wed.)
Now one hour into tonight's make-or-break engine firing for Cassini to enter orbit around Saturn. Another 36 minutes remain.
0333 GMT (11:33 p.m. EDT Wed.)
Cassini's speed is nearing 66,000 mph as the probe flies 18,000 miles over the planet.
0331 GMT (11:31 p.m. EDT Wed.)
The communications signal is increasing as Cassini moves from behind the A ring. This communications window will continue for about six minutes in the gap between rings. Then Cassini will go behind the B ring as view from Earth, which could disrupt communications for 28 minutes.
0327 GMT (11:27 p.m. EDT Wed.)
Cassini is 20,500 miles over the cloud tops of Saturn, traveling at 64,400 mph.
0325 GMT (11:25 p.m. EDT Wed.)
Full-strength communications is expected to be restored at 0331 GMT when Cassini moves into position where it can see Earth through a large gap between the A and B rings of Saturn.
0324 GMT (11:24 p.m. EDT Wed.)
Cassini is now half-way through this engine firing.
0320 GMT (11:20 p.m. EDT Wed.)
During this 96.4-minute engine firing, Cassini will consume 1,874 pounds of rocket fuel, nearly a third of the 6,600 pounds loaded aboard the spacecraft for the mission.
0316 GMT (11:16 p.m. EDT Wed.)
Altitude is 25,000 miles above Saturn. Velocity is now 62,000 mph. The signal interruption because of the A ring continues. A few moments ago, however, controllers did receive a short blip from Cassini via a gap in the ring as predicted.
0312 GMT (11:12 p.m. EDT Wed.)
Now 36 minutes into the planned 96-minute orbit capture maneuver. A full hour of engine firing time is left to go.
0308 GMT (11:08 p.m. EDT Wed.)
Cassini's speed has increased to over 60,000 mph.
0308 GMT (11:08 p.m. EDT Wed.)
Signal disruption is occurring as expected due to the thick A ring that is between Cassini and Earth.
0306 GMT (11:06 p.m. EDT Wed.)
Cassini is now passing behind the A ring of Saturn as viewed from Earth. Communications outages is possible over the next 25 minutes during this passage behind the ring.
0303 GMT (11:03 p.m. EDT Wed.)
Altitude over Saturn is 32,000 miles with a speed of over 59,000 mph.
0259 GMT (10:59 p.m. EDT Wed.)
From Earth's view, Cassini is now passing behind the F ring.
0258 GMT (10:58 p.m. EDT Wed.)
Cassini is 35,000 miles above the cloud tops and traveling at 58,000 mph. The engine firing continues according to plan.
0254 GMT (10:54 p.m. EDT Wed.)
In about five minutes, Cassini will pass behind Saturn's F ring as seen from Earth. However, this is not expected to disrupt the communications link between the spacecraft and Earth.
0250 GMT (10:50 p.m. EDT Wed.)
The main engine being used tonight has a certified life of 700 minutes. So far in the 7-year flight from Earth to Saturn, the engine has fired just over 100 minutes. Another 96 minutes, if all goes well, will be put on the engine tonight during the insertion burn.
0246 GMT (10:46 p.m. EDT Wed.)
Ten minutes down, 86 minutes left to go in this orbit insertion burn. Controllers report the engine firing appears to be going normally.
0245 GMT (10:45 p.m. EDT Wed.)
Altitude is now 41,500 miles as Cassini speeds along at nearly 56,000 mph.
0242 GMT (10:42 p.m. EDT Wed.)
The spacecraft is about 43,000 miles above Saturn's cloud tops as the engine burn continues, mission control says.
0240 GMT (10:40 p.m. EDT Wed.)
Cassini is traveling at 55,000 mph. The speed is increasing because of Saturn's gravity pull despite the braking maneuver underway.
0236 GMT (10:36 p.m. EDT Wed.)
MAIN ENGINE START! NASA's Cassini spacecraft has ignited its main engine for a critical 96-minute rocket firing that will slow the probe by about 1,400 mph and allow Saturn's gravity to capture it into orbit. The maneuver must be performed successfully or else the craft will sail past the planet, dooming the mission.
Cassini is the most sophisticated robotic space probe ever built. It will orbit Saturn for a four-year tour of the planet, its remarkable rings and numerous moons.
0234 GMT (10:34 p.m. EDT Wed.)
The spacecraft has completed its turn to the burn attitude, controllers confirm.
0226 GMT (10:26 p.m. EDT Wed.)
A signal has been received from Cassini! The spacecraft has made it safely through the ring plane. The next heart-stopping moment will be the orbit insertion burn starting at 0236 GMT.
0222 GMT (10:22 p.m. EDT Wed.)
This turn should take about 10 minutes to complete. Ignition of the burn is 14 minutes away.
0221 GMT (10:21 p.m. EDT Wed.)
The spacecraft should be executing a turn from the protective ring plane passage orientation to the position for Saturn orbit insertion. Controllers expect to hear a tone from Cassini shortly, confirming the craft has survived the plane crossing and is in the engine firing position.
0218 GMT (10:18 p.m. EDT Wed.)
Cassini's velocity is now 51,000 mph.
0211 GMT (10:11 p.m. EDT Wed.)
Cassini should be ascending through Saturn's ring plane right now.
The spacecraft is flying from below, passing through the plane and will arrive above the planet's remarkable rings where the orbit insertion burn will be performed starting at 0236 GMT.
Later tonight, Cassini will make a descending pass through the ring plane.
0200 GMT (10:00 p.m. EDT Wed.)
Cassini is out of communication with Earth as expected for the ring plane crossing. The signal will be restored once the spacecraft turns to the engine firing position.
0145 GMT (9:45 p.m. EDT Wed.)
Earlier concerns about high winds at the Deep Space Network tracking station in Canberra, Australia have eased. If the winds had been too strong, the massive antenna needed to hear Cassini's signal tonight would have been stowed. But Canberra is up and operating tonight.
0111 GMT (9:11 p.m. EDT Wed.)
Cassini is now expected to begin turning itself to point the large dish-shaped High-Gain Antenna into the direction of travel. This maneuver is designed to use the antenna to shield the spacecraft of dust particles when it crosses through the plane of Saturn's rings an hour from now.
"The antenna is a graphite-epoxy structure, so it's quite rugged and very capable of withstanding the kinds of small dust grains that we believe might be in this region," says Robert Mitchell, Cassini program manager.
Although scientists are confident that Cassini will survive this encounter with the rings, officials acknowledge it is a risky moment.
After the ring plane passage at 0211 GMT, Cassini will turn itself again. That turn at 0221 GMT will orient the spacecraft in the proper position for the engine firing beginning at 0236 GMT.
0051 GMT (8:51 p.m. EDT Wed.)
Ignition of the orbit insertion burn is less than two hours away. At this point in Cassini's pre-programmed sequence, the spacecraft is scheduled to switch from its High-Gain Antenna to the Low-Gain Antenna for communications to Earth. This transition means that telemetry of spacecraft systems stops and ground controllers will receive only tones from Cassini. The tones will inform mission control that the craft safely crosses the ring plane and performs the full 96-minute engine firing tonight.
A detailed timeline of upcoming's events is available here.
WEDNESDAY, JUNE 30, 2004
2130 GMT (5:30 p.m. EDT)
As Cassini nears Saturn, the Russian and American astronauts living aboard the International Space Station have floated outside of their orbiting home today to replace a faulty circuit breaker box. We are posting live updates on the spacewalk here.
We will post live play-by-play reports of Cassini's orbit insertion burn beginning around 9 p.m. EDT (0100 GMT).
2040 GMT (4:40 p.m. EDT)
The Saturn orbit insertion engine firing by Cassini is about six hours away. Although this is considered a "braking maneuver" to enter orbit around the planet, Cassini's speed actually increases.
"Orbit insertion is sort of like applying your brakes while driving your car downhill," said Robert Mitchell, program manager for the Cassini-Huygens mission at JPL. "Although you've got your foot on the brakes, you still pick up speed as a steep gravity pulls you in."
During the burn, the spacecraft will change its velocity by 626 meters per second (1,400 miles per hour). Relative to Saturn, at burn start the spacecraft speed is 24.26 kilometers per second (54,270 miles per hour) and at the end of the burn the speed is 30.53 kilometers per second (68,293 miles per hour).
"Getting into orbit means we have a mission. If we don't get into orbit then we have a flyby and that's not what we are here to do," said Dr. Dennis Matson, project scientist for the Cassini-Huygens mission at NASA's Jet Propulsion Laboratory. "We are confident that the Cassini team will get us there."
1845 GMT (2:45 p.m. EDT)
Executing stored instructions, the electronic brain of NASA's Cassini probe made final preparations for a critical 96-minute rocket firing tonight that will slow the craft by about 1,400 mph and allow Saturn's gravity to pull it into orbit.
The make-or-break Saturn Orbit Insertion - SOI - maneuver was scheduled to begin at 10:36 p.m. EDT and end around 12:12 a.m. Thursday. If successful, the burn will put Cassini in a long orbit around Saturn, kicking off a four-year tour of the ringed planet, its magnetosphere, its largest moon, Titan, and a retinue of smaller, icy satellites.
If the rocket firing fails or falls short of its 96-minute target duration, the $3.3 billion spacecraft will sail past Saturn and into a useless orbit around the sun.
"Unlike the two Voyagers that flew by Saturn in the early '80s and obtained just days worth of Saturn close-in science, Cassini-Huygens will be for Saturn what the Galileo mission was for Jupiter: a long-term science observatory," said Ed Weiler, NASA's associate administrator for space science.
But, he cautioned, "we are not there yet. Although things have gone very, very well so far, Saturn orbit injection will be the most critical event in the mission's life since launch. This main engine burn must be performed as planned or the mission will be lost.
"Unlike the Mars (rover) landings, where we had the 'six minutes from hell,' so to speak, in this case it'll be 96 minutes in purgatory. I hope the outcome will be as successful as our experiences with the Mars missions last January."
Read our full story.
1630 GMT (12:30 p.m. EDT)
The Cassini spacecraft is healthy and on course as it races toward Saturn for tonight's rendezvous and orbit insertion maneuver.
As of 1600 GMT, the probe was 650,000 km from Saturn and traveling at a speed of 12 km/sec. By 2200 GMT tonight, Cassini will have cut the distance to 375,000 km while its velocity increases to 15 km/sec due to the effects of Saturn's gravity.
"We are feeling the gravity well. We are falling into Saturn very rapidly," Jeremy Jones, the navigation team chief, told reporters a short time ago from NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Cassini is operating on its pre-programmed script that will control the spacecraft through tonight's engine firing to enter orbit around Saturn.
"The spacecraft, the flight software and the onboard sequences are now completely self-contained and need no ground interaction from us to complete this burn," said Julie Webster, spacecraft team chief.
"This morning just after 7 a.m. (1400 GMT), the final heater states were set and the engine gimbals were turned on. The gimbals are the little actuators that actually control the rocket engine nozzle pointing.
"Just after 12:30 this afternoon (1930 GMT), we will perform an accelerator calibration. The accelerators sense the deceleration of the burn and tell when it is time to cut off the burn. And we will pre-aim the rocket nozzles so they are in the direction we need them to be in for the burn."
Cassini is currently pointed at Earth and sending mission control information on its status.
"We are continually monitoring the spacecraft health and safety, and we will do so until 6:14 this evening (0114 GMT) when we turn the spacecraft to the ascending ring plane crossing attitude and we lose constant spacecraft contact."
Ignition of the burn is scheduled for 0236 GMT. A detailed timeline of today's events is available here.
0401 GMT (12:01 a.m. EDT)
This is a big day for planetary exploration. The Cassini spacecraft arrives at Saturn and must perform a 96-minute engine firing to enter orbit around the ringed planet. If the maneuver is not successful, the probe will sail past the planet and ruin the $3.3 billion mission.
"Everything has to go just right. The burn must occur for all 96 minutes, the turns must occur at the right time, the computers must keep the sequence going even in the event something unexpected should happen," said Robert Mitchell, program manager for the Cassini-Huygens mission at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
"The spacecraft has been programmed to continue even in the event of an emergency. With a one-way light time of 1 hour and 24 minutes, we had to teach the spacecraft to take care of itself. We don't want Cassini to call home if a problem arises, we want it to keep going. That is precisely what we've told the spacecraft: Don't stop, keep going until you've put in all 96 minutes of burn."
We will provide live play-by-play updates during the Saturn Orbit Insertion maneuver.
TUESDAY, JUNE 29, 2004
After a seven-year voyage from Earth, NASA's $3.3 billion Cassini probe is racing toward a make-or-break rocket firing Wednesday, a 96-minute maneuver designed to put the craft in orbit around the ringed planet Saturn for a four-year scientific odyssey.
Flight controllers at NASA's Jet Propulsion Laboratory in Pasadena, Calif., sent final commands to Cassini over the weekend, setting the stage for main engine ignition at 10:35:42 p.m. EDT (0235:42 GMT).
Operating more than 930 million miles from Earth - so far it takes radio signals an hour and 23 minutes to make a one-way trip - Cassini's on-board computer system must carry out the all-important rocket firing on its own.
At this point, flight controllers can only sit and wait. And chew their nails.
"I think about the Cassini mission as having three primary segments and then two rather hair-graying events that connect those segments into one continuous mission," said project manager Bob Mitchell. "The segments are designing and building the spacecraft, flying the spacecraft to Saturn and then conducting the science mission at Saturn.
"And the hair graying events are launch and orbit insertion, which is coming up tomorrow. Now for the launch event, I think we've all recovered from that very nicely, primarily because it was just so outstandingly successful. ... We're about to go through our second hair-graying event."
Read our arrival preview story from today.