Landsat 7 Satellite Might Be Dead

Lord Satri writes "Landsat 7 ETM+ remote sensing satellite, probably the most important Earth Observation satellite, might be dead now. This would have very important repercussions on the remote sensing / space community."

Comments

Re:"very important repercussions" ?

[speleo]

...I'm no asstronomer (sic)...

This is just a wild guess, but the Landsat 7 satellite ran by the US Geological Survey probably doesn't have much to do with astronomy...

Oh, yeah, suuuuure it's "dead"

[stanwirth]

During the Reagan administration, when a high-resolution statellite instrument to measure the earth's geoid and topography was suddenly found to be extremely useful in locating submerged submarines (by way of their wakes) it, too, suddenly "went dead." I knew the guy at Lamont-Doherty Geophysical Lab who discovered how to recover the submarine wakes from these data. Funny how only the high-res instrument (the one that could detect submarine wakes) suddenly "went dead." The low-res instrument continued to return data. It was an open secret in the geophysical community that the high-res instrument didn't actually have a malfunction. Funny how the US won the cold war with a few years after that, too. Hrmmm.

It was also the Reagan administration that privatised LandSat -- after spending billions of taxpayer's dollars to develop and deploy the LandSat satellites and do additional TM work from the space shuttle, suddenly all of the imagery was owned by a private company. And government-sponsored projects, instead of paying like $350.00 per scene, suddenly had to spend $3500.00 per scene. Double that to account for "University Overhead." What I want to know is, why, after paying for the development and deployment of this technology, do we (as taxpayers) then have to pay for it again when a project is formed to analyse these data? Didn't seem right at the time. Still doesn't seem right.

But I honestly doubt the LandSat 7 TM instrument actually went dead. It was probably found to be returning data of military significance, and why bother with the political rigamarole with the scientific research community, not to mention the delay involved with classifying data -- when you can just claim the thing "went dead"? After all, who is going to make the trip to the thing itself to verify the claim that it "went dead"?

Unreleased image == BINGO!

[RobertB-DC]

The US government already has 24 hours to review every image taken by US-owned spacecraft and decide whether or not to make them available based on national security concerns; there's no need to completely shut the thing down.

Not to become a conspiracy nut myself, but there are a couple of big problems with this defense:

One: There are a bazillion (I counted) satellites returning imagery, and probably not a bazillion folks to look over all the images before they're released -- especially not in a 24-hour timeframe.

Two: The withholding of any particular image or set of images is an immediate sign that the image contained useful information.

Assuming this satellite's data was discovered to contain militarily (or commercially!) useful information, the only way to keep both the imagery and its location secret would be to make all imagery unavailable for some reason.

This is the perfect conspiracy theory: it's almost entirely plausible, almost impossible to refute, and we want to believe it!

On the other hand, I can get a pretty good aerial view of Downtown Baghdad any time I want it.

LandSat 7 resolution

[Valdrax]

I'm chiming in in agreeance with the AC who says that you've never worked with LandSat 7 data. In my job as a developer for a company whose product line is used to analyze satellite and aerial photography, I regularly do. The LandSat 7 satellite has poor resolution for this sort of thing.

The color bands only have a resolution of 30 meters per pixel width, with the exception of band 6 (the far infrared band) which only has a resolution of 60 meters per pixel width. The panchromatic band has a better resolution of 15 meters per pixel width. If you do the math, that means that the color bands have a resolution of about a 1/6 of a football field per pixel.

This is nothing compared to other satellites out there. Orbital Imaging owns a satellite called OrbView-3 that should be going up soon which has an 4-band multispectral sensor with 4 m resolution on each band and a panchromatic sensor with 1 m resolution. Digital globe has 2.44 m multispectral data and 61 cm panchromatic data for sale as their basic imagery for sale. Trust me, LandSat 7 one of the least likely sensors to be shut down for being just "too good."

Your conspiracy theory is silly. As noted by another poster, the government already reserves the right to pull all sensitive information from it. This is routine. There's no reason to declare the satellite to be an expensive piece of space junk when they've already got procedures for handling data of military significance.

(BTW, the LandSat fleet was taken back under the government's wing in 1992 after the costs for data became too onerous.)

Re:LandSat 7 resolution

[stanwirth]

Actually, I worked on several image processing projects for the military, and we certainly did use LandSat data. And SPOT data (optical band) and SAR data (K band and X band mostly) as well as IR data.

The advantage of LandSat data is the broad spectrum of data returned, not the resolution. As a consequence, LandSat data alone has little tactical use, but it has tremendous strategic value -- particularly when geolocated and registered with data in other bands, and in conjunction with other data. In one project I did for the Comprehensive Test Ban Treaty Verification Organisation in Geneva, the challenge was to develop criteria for distinguishing mining sites from non-mining sites using satellite imagery. What does this have to do with A-tests? you may wonder. An underground explosion could be part of a mining or roadworks operation, or it could be a nuke test.

You've got the location of the explosion easily enough from the seismics, and it's easy enough to distinguish from an earthquake by its distinctive P/S wave ratio (explosions have almost no shear wave component, it's all compressional). Now how can you tell if its an ongoing mining operation without actually visiting the site? First you geolocate and register your LandSat, SAR, AVHRR and SPOT data to each other in the region of interest. Throw in some vector road maps and topography while you're at it. Imagery from different days, months, years, decades in the same area is also quite useful. Now you can either sit down an analyst in front of the data, or you can develop algorithms for identifying mining sites from various combinations of imagery. When you're done, let me know. LandSat data is tuned for collecting land-use information. Tree cover, grasslands vs. exposed rock for example. Clearings in the jungle that weren't there before. Desert areas that suddenly change to vast warehouse complexes well away from the largest roads and typical commerical trucking routes. Get the picture?

It is of tremendous strategic value to unobtrusively monitor land use over time, over large areas, for all sorts of military applications. Other data are better for tactical applications in a silly little game of soldiers, true--but you're not going to even want that level of resolution and targeting for determining new developments. The world is a big place. Where do you look first, and what kinds of anomalies do you look for? What anomalies are potentially of strategic significance? Quick, give the answer without LandSat data. Not as easy now, is it?

And as for calling it a "conspiracy theory" -- it's rather well known that there exist American satellites that have been said to have malfunctioned that have certainly not, because the data being returned was found to have military, strategic or other significance. The LandSat 7 "malfunction" could well be another instance. No conspiracy there. Satellites go black for different reasons. Malfunction is just one of them.

Look at it this way. I leave five dollars on my desk and it disappears. The thief is caught on camera and given a warning. A week later I leave five dollars on my desk again, and, again it disappears -- but this time the thief is not caught on camera. Is it "a conspiracy theory" to say, well, this guy was caught stealing once, and he was in the area at the time, so of course we're going to question him. Does calling this reasonable suspicion based on past behaviour a "conspiracy theory" wash? No. It's just simple inductive logic. Get over it.

LandSat 7: coverage and timing vs resolution

[stanwirth]

LandSat 7 is simply not as capable of a sensor as some of the others out there. Shutting it down without shutting down better sensors is wasterful and strategically pointless.

I'm not sure about that. For one thing, it's more plausible for an old satellite to "malfunction" than a new one. The other thing you need to consider is timing and coverage. Just because satellite A is better than B doesn't mean that it will be where you need the data at a particular time. No matter how you slice it, the data volume and coverage from A+B > the volume and coverage from A, unless the data from B is literally worse than useless.

Your "simple inductive logic" reminds me of an old joke: A mathematician, a physicist and an engineer ...

I know. That's why I identified formulating projections on the basis of past known events as inductive logic, rather than deductive logic. We're calculating probability density functions here, not proving that something is definitely so or not so.

By the way, can you give any substaniated examples of a satellite being shut down permanently when it was putting out data of military significance?

Yup! SeaSAT failed after 116 (or 106, or 99, depending on which source you believe) days of operation. The person doing the analysis showed me the pictures. I was just an undergraduate at the time. The high-res SAR data stopped coming through well before the low-res -- odd, considering the failure of the satellite was attributed to a massive power failure. The data were militarily significant for the better coverage of ocean floor topography than was practically feasible to gather with sonar -- again, coverage is key here, not resolution. Sonar gives you better resolution, satellite geoid and topography gives you better coverage, particularly in areas where it's difficult to conduct bathymetric surveys--around Novaya Zemlaya for example. Subsurface topography is the widely acknowledged military significance of these data. The person doing the analysis was specifically asked to decimate these data prior to publication-- remove the spikes. Sub holes, strategic canyons and particularly "anthropogenic time-dependent spikes in the sea surface topography". Sub wakes. He did it. I would have, too.

The later GeoSAT satellite data were held by the US Navy and not declassified until after the Cold War.