Mystery object re-entering atmosphere may be Apollo booster A lost and forgotten piece of what was probably a rocket booster is set for a November 13 impact over the Indian Ocean, and it's got space boffins scrambling to make sure they capture the event. The mystery object, WT1109F, has a very eccentric orbit that takes it out to twice the Earth-Moon distance, and observations since it …
If it were predicted to land on Blightly, our esteemed local council CCTV operatives will no doubt be aligning their cameras skywards to gather evidence and NASA can expect a Fixed Penalty Notice for litter in the post, to be paid within 14 days or it will double.
A repeat offence will no doubt attract an ASBO or whatever
NASA wont pay the fine going from past experience
Re the Space junk that landed in Australia a few years ago they were Finned and billed for that by the local Australian Authority's
Never paid Eventually it was paid by a private individual not connected to NASA
from wilki
Skylab reentered Earth's atmosphere and disintegrated in 1979, with debris striking portions of Western Australia
and The station did not burn up as fast as NASA expected, however. Due to a 4% calculation error, debris landed southeast of Perth, Western Australia,[3]:371 and was found between Esperance and Rawlinna, from 31° to 34°S and 122° to 126°E, about 130–150 km radius around Balladonia. Residents and an airline pilot saw dozens of colorful fireworks-like flares as large pieces broke up in the atmosphere.[22] The Shire of Esperance facetiously fined NASA A$400 for littering, a fine which remained unpaid for 30 years.[26] The fine was paid in April 2009, when radio show host Scott Barley of Highway Radio raised the funds from his morning show listeners and paid the fine on behalf of NASA.
"Why can't they see what this thing is? They were able to see missing tiles on a space shuttle in space in the early 1980s. Surely they can see a huge booster with 2015 technology?"
Two reasons:
1) As noted by others, distance. This isn't a target passing 200 miles over a USAF telescope in Florida.
2) Size. As noted by the article, this is not a "a huge booster," it's a ~1-2 meter panel.
Another point: While telescopes were aimed at STS-1, they couldn't see squat, or missing tiles for that matter. The following pictures are examples of terrestrial imaging of the shuttle during the 1980s and 1990s.
USAF Maui telescope (AMOS) image of a shuttle.
USAF 48-inch telescope in Florida, looking at STS-37
Civilian 90-inch telescope looking at Mir alone
These are probably the best effort for looking at the shuttle with more modern hardware. Mir-STS-37, and then the shuttle alone.
In any case, the telescopes used on STS-1 were incapable of spotting missing tiles, though NASA did request their aid in the hopes that maybe tile damage could be seen.
While supposedly spy satellites were used in the effort to examine Columbia's tiles, STS-1 commander John Young denied that a KH-11 Keyhole satellite was involved.
Anyway, back to Apollo hardware: it's a small item, not a huge booster, and it's much further away than the shuttle.
Astronomers reckon the object was probably knocked into its current orbit by the Sun's and Moon's gravity.
Can anyone explain, please, how the Sun's and Moon's gravity can knock something out of more normal Earth orbit? Or why lots of other stuff in orbit is not similarly sent off half way to the Moon?
They're not saying that the object was knocked into an Earth/Moon orbit, just that this is where its orbit currently is. They suspect that the Sun & Moon's gravity have acted (over time) to alter its orbit so it comes closer to Earth and gets caught in Earth's gravity permanently
You may want to read up about the three body problem. TL;DR - It's flipping hard to predict the orbits of three bodies circling each other. (And this is a four body problem which, of course, is even harder!)
"Can anyone explain, please, how the Sun's and Moon's gravity can knock something out of more normal Earth orbit? Or why lots of other stuff in orbit is not similarly sent off half way to the Moon?"
This panel from an Apollo mission was probably ejected after the third stage's burn toward lunar orbit, so it was already on a highly elliptical orbit.
Depending on altitude, there are a myriad of influences on satellite orbits:
1) Atmospheric drag
2) Earth's equatorial bulge. This is a big lump of mass outside the simple spherical model of Earth's mass that pulls and tugs on satellite orbits. See: nodal precession, and see lunar frozen orbits.
3) Light pressure. While only about 5 pounds per square mile, this is a long-term headache for space probes, geosynchronous satellites (especially comm sats and their big solar arrays), and medium altitude satellites outside the influence of Earth's atmosphere.
4) Gravity from other bodies, primarily the moon and then the Sun. These tend to be long-term issues for high altitude satellites.
Scroll about half way down to "Orbital Perturbations" for details. Wiki is more expansive explaining stationkeeping for satellites. They're actually battered all over the place by the sun, moon, light pressure, Earth's spare tire, and so on. Wiki's table of stationkeeping delta-V gives some detail on the magnitude of the problem keeping a satellite in its assigned orbit.
Basically, a lightweight aluminum panel from a Saturn IVB would be kicked all over the place by light pressure, and solar and lunar gravity. It's a solar sail with no control or stationkeeping motors. Boeing was just bragging about its "all electric" communication satellite that could use entirely ion motors for stationkeeping in GEO, and that is significant: it's a battle of about 50m/s per year to keep a communication satellite in its assigned geosynchronous slot. Barring unusual hardware failure, the life a comm sat is defined entirely by its fuel reserves. Going to all ion-type motors can let a very expensive comm sat continue generating revenue for twice as long.
The moon is particularly nasty for low-orbiting satellites. It has a very uneven gravity field and low-orbiting satellites tend to be perturbed into surface-intersecting flight paths in just a few months unless the satellites spend a lot of fuel keeping station. It was dumb luck that Apollo 15's sub-satellite was placed into what's known as a frozen orbit" and lasted 1.5 years, but Apollo 16's sub-satellite only lasted 35 days before performing an unscheduled and aggressive lithobraking maneuver.
The short version of all that: satellites don't stay in quiet, simple orbits driven only by Earth's gravity. Over the long run, small effects like light pressure and lunar gravity can deeply perturb orbits, especially those of high-orbiting satellites.
> Maybe the blame lies with the co-author(s).
Regrettably that's usually the case. When a Big Name Author starts franchising out the writing to someone else, it's never as good.
What's really galling is when you get caught by a Bait-and-Switch with the famous name in big bright letters on the front and the co-author's name in tiny, dark letters somewhere underneath and you don't realise it until after you've handed over the money :-(
@ Graham Marsden, Yep, having waited so long for the sequel to appear, I was very disappointed with the eventual release, far too much psychobabble and soap opera. When you think of the classic hard sci-fi that Clarke had previously produced, the follow-up to Rama could have been so good :-(
Clarke produced little that could be termed 'hard SF', even in his early days.
He did, however, write a rather primal paper on geosynchronous satellites, for the British Interplanetary Society, almost 20 years before there were any. I recommend all here read it.
Which makes him a superboffin at the time.
As a writer, too often a fantacist, a very few short stories may be accurately described as 'hard SF', but the bulk was most certainly not. The later Baxter collaborations descend to barely readable at times.
One of those was almost directly copied from a short story from Damon Knight, can't be bothered to check the spelling now. Title was The Light of other Days or similar.
Disgraceful copying.
although one of the astronomers watching it, NASA Jet Propulsion Laboratory's Bill Gray, suggests he “would not necessarily want to be going fishing directly underneath it”.
I'd have thought it'd be quite safe to be underneath it for most of its descent. It's only when it drops below 50 metres or so that it might present a risk.
Low mass? Hollow??
How'd they work that one out?
*****
They know roughly the strength and direction of the gravity field the object should be experiencing that close to the moon.
Mass can be worked out if you know the velocity of an object and measure how that velocity is changed by the gravity field it's traveling in.
Hollowness is simply based on the apparent size of the object compared to what they think it's mass is based on known densities of different materials the object might be made of.
"How'd they work that one out?"
Probably watching course deviations attributable to sunlight pressure (and subtracting influences due to the Earth, sun, and moon). They have a good idea of the object's albedo (reflectiveness) and its size, so astronomers can make a good guess about the force of sunlight being applied to it. Based on course deviations, you determine acceleration. With Force and Acceleration, mass is easy to estimate: (F = MA --> M = F/A).
Sunlight pressure is a major influence on low density satellites, like the Echo-1, Echo-2, and PasComSat. NASA learned a lot about solar sailing by watching those balloons wobble around low Earth orbit.
Bridgekeeper: "What is the object re-entering Earth's atmosphere on November 13???"
Arthur: "What do you mean? U.S. or Soviet object?"
Bridgekeeper: "I... I don't know that - AUUUUGH!"
Arthur: "Well, you have to know these when you're a king, you know..."
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