10 comments

• David K

  April 12, 2021 at 6:32 pm

  Very exciting!

  I wish that more companies would plan in this kind of life extension option from the design stage
• Col Beausabre

  April 13, 2021 at 2:40 am

  I think eventually all companies will. Now we just need a standard port design. There is a precedent. The navies of the world have agreed on a standard hatch design for both submarines and rescue devices and submersibles so any countries’ rescue equipment can rescue any countries’ crews. Obviously this only works for subs that bottomed above their crush depth and in the case of the Kursk the refusal of the Russian government to accept the aid of any other country until it was too late doomed the survivors located aft. Thank you, Mr Putin
• markedup2

  April 13, 2021 at 9:07 am

  There may be too much ignorance in this post to deal with, so feel free to ignore me. I don’t understand the perspective of this picture and/or the orientation of the satellite.

  As I understand it, satellite orientation is usually done via gyroscopes. So, spinning one about is basically free as long as the gyros keep spinning. It is thruster propellant that runs out. Station keeping thrust is _mostly_ along the orbital path to either slow it down or speed it up.

  The long flat things are the solar panels. Are the covered-with-a-garbage-bag things the antennae? The reason I ask: If so, it appears that the antennae are pointed in the right direction (toward Earth), but that puts the thrust direction “down” toward Earth. Why would one want thrust in that direction? If the satellite was rotated for the rendezvous, did the antennae also rotate in order to not lose service? Their position looks “nominal” in that they are “squared up” with the shape of the satellite body.

  I’m also trying to figure out the orientation of the solar panels. While the satellite could be illuminated by the servicing one, clearly the Earth is not. That must be sunlight (or Earth’s night-time IR signature is much more detailed than I expect it to be, which is certainly possible). Being in geosynch, the sun rotates around it (from its own perspective). Do the panels rotate, too? That seems like an equipment failure waiting to happen. Or do we just accept that they are shaded by themselves for parts of the day? In which case, they would have their functional surface facing in opposite directions so one would be in the sun while the other was shaded. Or is it even simpler: Both surfaces are functional?

  Thanks for any help.
• Andi

  April 13, 2021 at 11:41 am

  It’s possible that the engine nozzle to which MEV-2 attaches is the apogee kick motor nozzle rather than the thrusters. Thruster output nozzles tend to be quite small. Once the geosynchronous orbit is established, the satellite would be rotated to its optimal attitude.
• Max

  April 13, 2021 at 9:13 pm

  They always place the thruster on the opposite end, far away of the important stuff. You can’t have engine flame melting your panels or antennae.
  MEV-2 must connect to the thruster because it is the most secure and available protrusion to latch onto prevent any damage elsewhere. Very convenient and logical. If it parked and clamp down to the satellite from the front, it would block all signals rendering the satellite useless.
  It appears the solar panels are made to rotate? to follow the sun. MEV-2 has its own solar panels, gyroscopes, thrusters for its five year mission of extending a geosynchronous satellites life a few years more. (no matter how well-made, the harsh light and radiation in space degrades solar panels quickly giving them less than a 20 year half life-span) Essentially it’s just a hospice nurse / tow truck for space.

  It could be utilized for more, like hijacking the data the satellite receives… corrupting the data? In which case spy satellites may pick up a hitchhiker that they were unaware of… With a self-destruct thermite, appearing like astroid damage, when a country needs the satellite the most…

  After the five year mission, MEV-2 will disconnect so IS-10-02 can rotate, fire it’s engine (if it has any fuel left) and park it’s self in a graveyard orbit. If it can’t do this, MEV-2 can help it.
  MEV-2’s next mission, if everything goes as expected, may already be in the graveyard orbit anyway.

  Space is cold, it makes sense that they would use a infrared camera to locate any heat signature of a small object in the vast black sky.
  The satellite is over the equator and it looks like African Sahara? below. I find it interesting that clouds, which are described as a blanket, has no heat signature being cold.
  Earth being warm and emitting heat is not a surprise, all the planets, except a few, broadcast more heat into space than they receive from the sun. Even Antarctica, which averages -70° during its six months of winter, is over 200° warmer than outer space above it. The polar region of the moon, on the other hand, is near 400° below zero, 100 degrees colder then Earth’s shadow making it as cold as Pluto, much colder than anywhere on Mars.
  My knowledge is limited but I’ve learned much on this website. I hope this helps.
• Edward

  April 13, 2021 at 11:24 pm

  I have worked on building and testing several commercial communication satellites. In fact, I worked in the next hi-bay over from the Intelsat 901 that was last year’s target; I thought I would never see it again, but there it was.

  The satellite is in operational orientation, which is to say that the main engine, the liquid apogee engine (a liquid version to solid rocket kick-motors), is facing the docking spacecraft and faces away from the Earth during operation. When circularizing the orbit shortly after launch, it points toward the west and increases the eastward speed, raising the perigee to be the same as the apogee. Then the satellite is reoriented to “face” the Earth, and this engine is not intended to be used again, with the possible exception of raising the orbit to the graveyard orbit at the end of the satellite’s life — the station keeping thrusters are capable of performing this maneuver.

  On the far side of the spacecraft is what is usually called the Earth Deck of the spacecraft. It faces the Earth and has various equipment and antennas that require a view of the Earth. The Earth is dimly visible in the background of the picture. The larger ring feature that you see around the engine is the interface ring, used to mount the satellite to the launch vehicle, and it is a standard mount for these types of satellites. These large communication satellites are attached much differently than the Starlink satellites that we see in the Falcon 9 launch videos. The MEVs use the main engine as well as this ring to connect to the target satellite.

  These satellites almost always use momentum wheels or reaction wheels for orientation (the gyros measure the orientation, and the reaction wheels change or maintain the orientation). Because the satellite is revolving around the Earth, it only looks stationary when viewed from the rotating Earth, its orientation relative to the universe constantly changes, so the reaction wheels are constantly spinning faster and faster with each orbit. Every once in a while, small thrusters are fired in order to cause a counter-torque to allow the wheels to slow down, and the process begins again. The thrusters are not the primary means of orientation, as they would have to fire far more often than desirable, since getting the rotation exactly right is far harder to do with thrusters than with wheels. These thrusters are generally located at or near the eight corners of the satellite and point in three directions at each corner, allowing for station keeping as well as orientation maintenance. Generally, these are low thrust, such as 1 lb. or 5 lb. thrusters (or a combination), and they use the same propellant tanks that the liquid apogee engine used.

  Surprisingly, most thruster station keeping is done for north/south station keeping. Forward/backward and up/down (toward or away from Earth) is not as greatly affected by the Moon and the Sun, but these two bodies constantly pull in the north or south directions quite a bit for two weeks or six months before switching direction. There are special thrusters with high Isp (efficiency) that occasionally correct for this motion. Hall Effect Thrusters (specialized ion thrusters) have become popular for this purpose. Geostationary satellites do not experience air drag, unlike low Earth orbiting satellites, such as the space station.

  The solar panels, the long, flat “wings” that extend beyond the edge of the photograph, are oriented north/south. The top of the photograph is either north or south. Only one surface is functional as a power collector, the other surface is used to radiate away the heat lost due to the less-than-100% efficiency of solar arrays. They rotate relative to the satellite once a day, as the satellite goes around the Earth once a day, in order to keep pointing toward the Sun, but they rotate relative to the fixed universe once a year, as the Earth goes around the Sun. Being on the north and south sides prevents them from being shaded by the spacecraft. Near the equinoxes (March/April and September October), the Earth occasionally shades the satellites, so they have batteries that allow them to operate at full capacity during those times in the Earths umbra. The MEV spacecraft solar arrays will experience an extra daily eclipse of the sun due to the target satellite’s solar arrays, but that is accounted for in the planning phase of the mission. Ultraviolet light tends to degrade solar panels, and their power generation is accounted for in end-of-life planning for each satellite. If they want full operational capability at the end of life, then more panels are necessary. Otherwise fewer can accommodate the owner’s needs.

  The Solar Array Drive Assemblies are reliable and do not often fail. However, as with all other parts of the satellite, insurance can be purchased to cover losses of service due to such failures. Insurance companies are eager that all parts of a satellite are reliable. Because the north and south sides of the satellite are pointed at 90 degrees (well, more like 68 degrees, because of the angle of the equator to the orbit of the Earth) from the Sun, they don’t get heated by direct sunlight, so they are used as radiators to remove the heat generated by all the equipment on the satellite.

  The “garbage bag” things are the reflector part of the antennas. The baggy parts are thermal blankets, there to help prevent thermal distortion of the reflectors. The opposite side, the reflective side, has an expensive coating that does a similar job of thermal control, but the back side is cheaper to put on a blanket. There is a feed horn at or near the Earth Deck that broadcasts at each reflector, and the reflectors are shaped so that the broadcast on Earth is only seen by the countries that allow that satellite’s broadcasts. For instance, Cuba is not happy to receive most broadcasts intended for Florida, 90 miles away, so the reflective surface is shaped so that the power of the broadcast only goes where it is wanted. The reflectors are located in the direction of travel (the east side of the satellite) and in the opposite side (the west side). Thus, five of the six sides are functional sides. MEV docks itself to the sixth side.

  For the rendezvous with Intellsat 10-02, the satellite almost certainly remained operational, or at least in operational orientation, for minimal disruption of service.

  I hope this clearly answered the questions. If you still have questions or come up with other questions, please ask.
• pawn

  April 14, 2021 at 7:28 am

  Thanks Edward. That was very good of you to explain these things.
• Max

  April 14, 2021 at 1:12 pm

  See what I mean when I say “I’ve learned much from this website?”
  Thanks Edward.
• Robert Zimmerman

  April 14, 2021 at 1:50 pm

  Max. Me too, even though I write it. Thanks to Edward as well.
• markedup2

  April 25, 2021 at 8:14 am

  A late check back for answers and what a marvelous surprise! Thank you for such a detailed explanation!