Friday, September 23, 2011

UARS UPDATE 09-23-2011 at 11:49pm:NASA Update # 13 Working On New "Re-entry Location". (Becoming A Joke On Twitter)

NASA Update #13
Fri, 23 Sep 2011 10:55:17 PM MDT

As of 10:30 p.m. EDT on Sept. 23, 2011, the orbit of UARS was 85 miles by 90 miles (135 km by 140 km). Re-entry was expected between 11:45 p.m. Friday, Sept. 23, and 12:45 a.m., Sept. 24, Eastern Daylight Time (3:45 a.m. to 4:45 a.m. GMT). During that time period, the satellite was passing over Canada and Africa, as well as vast areas of the Pacific, Atlantic and Indian oceans. The risk to public safety was very remote. NASA is working to confirm the re-entry location and time and will provide an update shortly.
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A 6-ton NASA satellite on a collision course with Earth clung to space Friday, apparently flipping position in its ever-lower orbit and stalling its death plunge.

The old research spacecraft was targeted to crash through the atmosphere sometime Friday night or early Saturday, putting Canada and Africa in the potential crosshairs, although most of the satellite should burn up during re-entry. The United States wasn't entirely out of the woods; the possible strike zone skirted Washington state.

"It just doesn't want to come down," said Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics.

McDowell said the satellite's delayed demise demonstrates how unreliable predictions can be. That said, "the best guess is that it will still splash in the ocean, just because there's more ocean out there."

Until Friday, increased solar activity was causing the atmosphere to expand and the 35-foot, bus-size satellite to free fall more quickly. But late Friday morning, NASA said the sun was no longer the major factor in the rate of descent and that the satellite's position, shape or both had changed by the time it slipped down to a 100-mile orbit.

"In the last 24 hours, something has happened to the spacecraft," said NASA orbital debris scientist Mark Matney.

On Friday night, NASA said it expected the satellite to come crashing down between 11:45 p.m. and 12:45 a.m. EDT Saturday. It was going to be passing over the Atlantic, Pacific and Indian oceans at that time, as well as Canada and Africa.

"The risk to public safety is very remote," NASA said in a statement.

Any surviving wreckage is expected to be limited to a 500-mile swath.

The Upper Atmosphere Research Satellite, or UARS, will be the biggest NASA spacecraft to crash back to Earth, uncontrolled, since the post-Apollo 75-ton Skylab space station and the more than 10-ton Pegasus 2 satellite, both in 1979.

Read more:

UARS SIGHTED OVER TEXAS: UARS is still in orbit. Observers in central Texas saw it streaking overhead (but not disintegrating) at 8:18 PM CDT on Sept. 23rd (1:18 UTC on Sept 24th). images: from Adrian New of San Antonio, Texas

UARS Tracking Resources:

UARS UPDATE 09-23-2011 at 9:00pm GMT: 
0220 GMT (10:20 p.m. EDT Fri.)
Strategic Command's final prediction has been issued for re-entry at approximately 12:16 a.m. EDT (0416 GMT). The satellite would be approaching the coast of North America at that time, crossing Washington before flying over Canada. But the margin of error remains plus or minus two hours.
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UARS UPDATE 09-23-2011 at 6:50pm GMT:
Pilots Receive Warning...
The Federal Aviation Administration issued an alert to pilots today warning flyers to be on the lookout for any signs of a huge NASA satellite expected to fall to Earth tonight or early tomorrow.

FAA officials released the special notice after NASA refined its estimates for the re-entry time of its Upper Atmosphere Research Satellite (UARS), a 20-year-old climate satellite the size of a school bus that will fall from space sometime in the next 18 hours.

"Aircraft are advised that a potential hazard may occur due to re-entry of satellite UARS into the Earth's atmosphere," the FAA said in the statement. "FAA is working with the Department of Defense and NASA to ensure the most current re-entry information is provided to operators as quickly as possible."

NASA and the U.S. military's Space Surveillance Network still do not know exactly where the UARS satellite will fall when it hits Earth's atmosphere. Earlier this week, NASA scientists predicted that the satellite would miss North America altogether, but the space agency announced today that there is a slight chance that the 6-ton spacecraft could fall over the United States.

FAA officials told pilots to keep an eye out for any fireballs or other signs of the satellite's re-entry.

"In the interest of flight safety, it is critical that all pilots/flight crew members report any observed falling space debris to the appropriate (air traffic control) facility and include position, altitude, time and direction of debris observed."

Any pilots, flight crew members or aircraft passengers who manage to observe the UARS satellite re-entry could get a spectacular view. Because the satellite is so large, its fiery re-entry should be visible as a bright fireball, even in daylight. If the satellite falls over the Earth's night side, the resulting light show could be spectacular, NASA officials have said.
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UARS UPDATE 09-23-2011 1PM GMT
As of 10:30 a.m. EDT on Sept. 23, 2011, the orbit of UARS was 100 miles by 105 miles (160 km by 170 km). Re-entry is expected late Friday, Sept. 23, or early Saturday, Sept. 24, Eastern Daylight Time. Solar activity is no longer the major factor in the satellite’s rate of descent. The satellite’s orientation or configuration apparently has changed, and that is now slowing its descent.

There is a low probability any debris that survives re-entry will land in the United States, but the possibility cannot be discounted because of this changing rate of descent. It is still too early to predict the time and location of re-entry with any certainty, but predictions will become more refined in the next 12 to 18 hours.

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Increased solar activity brings re-entry of UARS NASA satellite closer

Update (8.34 am AEST): I have just checked the visibilty updates for Australia for viewing the UARS satellite in our evening sky. Unfortunately the significant change in the satellites orbit due to solar heating of the upper atmosphere means these no longer exist. We now have to wait for updates from NASA regarding when the satellite will re-enter and hope it occurs over Australia. There are a number of daylight passes and I will be watching when I have the opportunity to see if it is visible. Watch this space (pun intended)!

Origional post: NASA has announced that recent solar activity has brought forward the likely re-entry date of the Upper Atmosphere Research Satellite to 24 September 2011 (plus or minus one day). The expected re-entry date was previously the end of this month or early October. The exact wording on the UARS site is ‘As of Sept. 15, 2011, the orbit of UARS was 143 mi by 158 mi (230 km by 255 km). Re-entry is expected Sept. 24, plus or minus a day’.  The exact time won’t be known until shortly before reentry. My previous post about the UARS re-entry can be found here.

Keep in mind that the UARS satellite is visible in Australian skies over the next couple of nights. Information about how to get viewing information can be found here.

Upper Atmosphere Research Satellite (UARS) Image courtesy NASA
The increased solar activity has heated the upper atmosphere resulting in it expanding. This has increased atmospheric drag on the satellite shortening its life further.

Orbital Decay - Altitude Prediction Graph

The prediction graph is a plot of perigee & apogee over time (thus dual lines) actual altitude oscillates 16 times per day.
There are three pairs of lines, the original prediction pair, the revised prediction (f=1.5) and the actual observed.

Updates on predicted re-entry times for UARS satellite

Predicted Reentry Time for UARS satellite as of September 22 10:06 CDT (15:06 UTC): September 23, 2011 5:07 p.m. CDT (22:07 UTC) ± 9 hours.
UPDATE SEPTEMBER 22, 2011 10:06 CDT (15:06 UTC) Predicted Reentry Time: September 23, 2011 5:07 p.m. CDT (22:07 UTC) ± 9 hours.

SEPTEMBER 22, 2011 5 CDT (10 UTC) NASA has now refined its prediction slightly for when this bus-sized satellite will fall to Earth. The predicted re-entry is now scheduled for 3 p.m. CDT (20:36 UTC) on September 23, 2011, plus or minus 20 hours.

It has been known for some time that the 6.5-ton satellite would leave orbit and return to Earth. Experts initially suggested a weeks-long window between late September and early October, then narrowed the window to the last week of this month. Later, NASA trimmed the interval to a three-day period centered on September 23.

Above is a somewhat disconcerting video – to me anyway – video showing the tumbling and clearly uncontrolled UARS satellite in orbit on September 15, 2011. It’s from Thierry Legault, a wonderful astrophotographer, who obtained this footage of UARS with his 14-inch telescope in northern France, when the satellite at an altitude of only 250 kilometers (155 miles) above Earth. You can see UARS body and its solar arrays.

The 20-year-old satellite – the Upper Atmosphere Research Satellite (UARS) – will make an uncontrolled re-entry through the Earth’s atmosphere. Pieces of the 6.5-ton satellite are expected to survive the fiery plunge and hit our planet, although no one knows exactly where.

Real time satellite tracking for UARS
UARS re-entry twitter feed

The chances of being hit by the falling UARS satellite are small. Nick Johnson, chief scientist with NASA’s Orbital Debris Program, told Universe Today last week:
Numerically, it comes out to a chance of one in 3,200 that one person anywhere in the world might be struck by a piece of debris.
When you think about the seven billion people on Earth today, you see how vanishingly small the probability of being struck really is. After all, most of Earth is ocean, so chances are UARS will go from the fires of re-entry directly to a watery grave in the ocean depths. It’s also important to note that no injury has ever been caused by orbital debris during the half-century that we humans have been placing objects in Earth orbit.

Tongue-in-cheek debris map for UARS re-entry developed by The
NASA says the satellite is likely to begin re-entry on September 23, 2011, give or take a day. Hurtling at five miles (eight kilometers) per second, they say it could land anywhere between 57 degrees N. latitude and 57 degrees S. latitude – basically, most of the populated world.

Doomed satellite: Where and when will it plummet to Earth?

It is still too early to tell exactly where the dead satellite will fall. Scientists will likely have a much better idea of where the debris will land about two hours before the impact, NASA officials said.

UARS Update: NASA Refines Crashing Satellite’s Debris Region and Location

by Nancy Atkinson on September 22, 2011

This video from Analytical Graphics, Inc. shows an updated animated analysis of the break up of the the 6 ton, bus-sized UARS satellite. It likely will burn up at an altitude between 80-45 kilometers, with an estimated 26 pieces of debris re-entering the atmosphere for land fall or splash down. The debris zone is predicted to be about 500 miles long.

The latest update on UARS put out by NASA is that as of 1:30 p.m. EDT Sept. 21, 2011, (17:30 GMT) the orbit of UARS was 120 mi by 130 mi (190 km by 205 km). Re-entry is expected sometime during the afternoon of Sept. 23, Eastern Daylight Time. NASA says the satellite will not be passing over North America during that time period, but that it is still too early to predict the time and location of re-entry with any more certainty. They will be able to further refine more details in the next 24 to 48 hours.

AGI has created an app for Android phones where you can track the UARS orbit track. See this link for more info.

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