[HN Gopher] End of an Era: Landsat 7 Decommissioned After 25 Yea...
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End of an Era: Landsat 7 Decommissioned After 25 Years of Earth
Observation
Author : keepamovin
Score : 101 points
Date : 2025-06-05 04:09 UTC (18 hours ago)
(HTM) web link (www.usgs.gov)
(TXT) w3m dump (www.usgs.gov)
| gnabgib wrote:
| Related: _End of an era: Landsat 7 mission takes final images_
| (273 points, 8 months ago, 48 comments)
| https://news.ycombinator.com/item?id=41663465
| mceoin wrote:
| We're reaching a history / pre-history moment where the entire
| earth's history will be available as a high definition orb with
| video feed, scrollable through time.
| jvanderbot wrote:
| Landsat is one of those (for now, bygone) projects that the US
| Gov (and EU!) ran to the benefit of basically everyone. Imagine
| the benefit for any kind of land planning to have access to this
| data. USGS.gov has tons of soil and topology data, thanks in
| large part to this program, and essentially free for all.
|
| Other programs we just never think about include NOAA state of
| the art weather from which all "local weather" is possible, free
| and open air navigation charts, and free air traffic control.
| Think about how, scattered across the entire continental USA,
| there are a dense network of radio towers broadcasting homing
| signals so that any aircraft can navigate safely without
| subscription or cost.
|
| And then of course we have GPS.
|
| It's just unbelievable the things we've built and essentially
| given away for the benefit of humanity. Apolitically, I look
| forward to an era where we can do that again (without living on
| borrowed time, if possible).
| larrled wrote:
| Most innovation is military innovation, if only by proxy.
| tonyhart7 wrote:
| *military and space
| Moto7451 wrote:
| The latter often is just for the former but with some PR.
| Not all but a significant amount. The first US and Soviet
| astronauts were flying ICBMs. Hubble is leftover spy
| satellite gear and two more leftover similar satellites
| were gifted to NASA in recent history. The Space Shuttle
| was intended to capture foreign satellites for the CIA. The
| Soviet Union had small space stations that carried cannons.
| And of course, we both nuked space just to make sure that
| worked.
|
| Clearly we do a lot more commercial space at this point but
| the lineage is there.
| PunchyHamster wrote:
| It is not "given away". It is an investment into economy that
| I'd imagine pays out very well all things considered.
| pqdbr wrote:
| I don't understand this: article states it will drift as space
| debris for 55 years (!) before reentering the atmosphere? Why
| isn't this done immediately by just lowering it's orbit even
| further and letting it burn?
|
| > The final steps included carefully lowering the satellite's
| orbit to decrease the risk of collisions and ensuring that all
| energy sources, such as fuel and batteries, are depleted to
| prevent the satellite from accidentally turning back on or
| creating debris. As Landsat 7 begins this decommissioned phase,
| it will drift silently in orbit for about 55 years before
| reentering Earth's atmosphere.
| sidewndr46 wrote:
| you would need to carry enough fuel on board to get rid of most
| of the velocity obtained during orbital insertion. That is lots
| of fuel
| perihelions wrote:
| > _" Why isn't this done immediately by just lowering it's
| orbit even further and letting it burn?"_
|
| It'd take a very significant and expensive amount of fuel to
| "just lower" the orbit! From its 700 km orbit, it'd cost (by my
| estimate) roughly 300 m/s, or on the order of 10% of entire
| satellite mass, to perform this lowering burn.
|
| It's not at all standard practice to deliberately dispose of
| satellites this way (SpaceX is a major outlier), and wasn't
| even on the radar in the 1990's, when this satellite was being
| built.
|
| (Here's an anchoring point: the projected cost for the
| propulsion to "just" deorbit the International Space Station,
| at the end of its operating life, is $1.5 billion [0]).
|
| [0] https://spacepolicyonline.com/news/nasa-iss-deorbit-
| vehicle-...
| bmacho wrote:
| > (Here's an anchoring point: the projected cost for the
| propulsion to "just" deorbit the International Space Station,
| at the end of its operating life, is $1.5 billion [0]).
|
| That's under 2% of the total cost, that's not too much, if
| you compare it to the rest of the TCO, and not how beneficial
| would it be.
| sitkack wrote:
| Should use the ISS as the base mass for a EM launcher.
| Seems nuts to waste so much on that existing potential
| energy.
| mandevil wrote:
| ISS is in a bad orbit for this sort of thing: halfway
| between the best orbit for Baikonur and the best orbit
| for Kennedy, it was a compromise which was okay because
| it wasn't getting that much traffic, so the penalty
| didn't amount to much at the scale of the budget. Using
| it as an orbital way-station will end up paying that
| compromise penalty a whole lot of times on all the
| launches up to the station, driving up the total value of
| the orbital penalty. If you are doing something big
| enough in space that you can afford to keep the ISS in
| operation (1) then you are probably better off building
| your own platform in the right orbit for your launch
| site. (2)
|
| Also, repeated dockings and undockings (as you assemble
| the mass driver and then use it) will ruin any
| microgravity experiments you might want to run, so you
| can't really combine "base station for deep space
| exploration" and "science lab" missions, you really need
| the station to be focused on one or the other.
|
| 1: The main problem ISS has is political, not
| technological. By design you need the US and Russia to
| cooperate to keep it operating, and that made a lot of
| sense in the 1990s, and has fallen apart over the past
| decade.
|
| 2: Orbital plane changes- to move ISS to the right orbit
| for a specific launch site- are hideously expensive in
| LEO. GEO satellites often find it cheaper to raise their
| apogee out to near the moon, make the necessary plane
| change way up high, and then drop the apogee again when
| they get to perigee, rather than make the plane changes
| in LEO. (ISS can't do that.)
| wat10000 wrote:
| It's in the ideal orbit for Baikonur. It's much, much
| easier for a low-latitude launch site to reach a high-
| inclination orbit than vice versa. This is especially
| true for Baikonur, where the available inclinations are
| restricted by human habitation and foreign countries
| downrange. Hence the minimum inclination is 51.6 degrees
| (which is where the ISS is) despite the launch pads being
| at 46 degrees latitude.
| mandevil wrote:
| You are correct, I had remembered the details wrong- ISS
| and Mir and Salyut 7 all have the same orbital
| inclination, so that's clearly the best orbit for
| Baikonur. So if you were doing your mass launches from
| Baikonur you would not pay much of a penalty. From KSC,
| though, you'd almost certainly want a lower inclination
| to get more payload up.
| wat10000 wrote:
| Really, you pay the same penalty launching to 51.6
| degrees regardless of whether it's Baikonur or KSC. But
| you're totally right, you can do even better by launching
| to lower inclinations out of KSC, which can go down to
| 28.6 degrees.
| tonyhart7 wrote:
| 1.5 billion??? if starship from space x is ready by the end
| of service. can we make it cheaper using starship? using
| robot arm or just push it to designated landing point with
| starship
| TimorousBestie wrote:
| This is basically what they're doing; most of the cost is
| for SpaceX to modify one of their existing vehicles into
| the USDV. You probably underestimate how much energy is
| needed to deorbit ISS.
| __m wrote:
| I wonder what the real costs are and what is taken as
| profit
| martinpw wrote:
| It seems to be a common misconception that lowering an
| object's orbit is much easier than raising it. I guess
| because it feels like it is just floating up there and
| gravity can do most of the work to pull it down if you give
| it a little nudge. In reality the energy required to lower
| the orbit is about the same as the energy required to raise
| it. In both cases you need to change the orbital velocity.
| notahacker wrote:
| > It's not at all standard practice to deliberately dispose
| of satellites this way (SpaceX is a major outlier), and
| wasn't even on the radar in the 1990's, when this satellite
| was being built.
|
| tbf it is _now_ a standard practice (quite literally: it 's
| part of ISO24113) for satellites in LEO to lower the orbit to
| allow reentry via natural orbital decay within 5 years or
| less (recently reduced from 25 years or less). Your average
| CubeSat launched into the lower reaches achieves this
| naturally through atmospheric drag without propulsion, but
| anyone sticking their satellite at 700km needs propulsion and
| sufficient total impulse to be able to conduct a deorbiting
| mission at end of life.
|
| But yeah, certainly wasn't in the 1990s when congestion of
| LEO wasn't a consideration
| wffurr wrote:
| I loved how early Landsat imagery featured in the movie Kong:
| Skull Island about finding a mysterious lost island in the
| Pacific.
| tinyplanets wrote:
| Off topic to the thread, but that was a surprisingly good
| movie!
| Animats wrote:
| Oh, good, there's still Landsat 8 and 9 working. The title
| suggested that perhaps this was part of a plan to cut down
| observations of climate change.
| mturmon wrote:
| not so good, see: https://news.ycombinator.com/item?id=44190279
| wewewedxfgdf wrote:
| Do these things continue to do their work, picturing and
| transmitting data, even after being decommissioned? Or do they
| need constant human attention and thus go silent?
| followben wrote:
| In 1990 I was super excited to have my high school work
| experience application accepted to CSIRO in Macquarie Park, only
| to find when I turned up that I'd spend the whole boring week
| cataloging magnetic tape from these dull satellites Landsat 4 &
| 5. The only time my greybeard supervisor seemed remotely animated
| was when he started imagining what imagery 6 & 7 would send back.
|
| How wrong I was; what this now greybeard wouldn't give to rummage
| through that lab again.
|
| RIP #7.
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(page generated 2025-06-05 23:01 UTC)