First modernized GPS satellite Launched

A reader writes "The first GPS 2R-M satellite has launched from Cape Canaveral, Florida on top of a Boeing Delta 2 rocket. The government is now competing with Europe's Galileo system, and has added two additional military channels and one civilian channel, which will increase the accuracy and performance of GPS - as well as increase its resistance to jamming."

Jamming by whom?

[moz25]

As I understand, one of the jamming related problems with GPS is not by criminals/terrorists, but by the government when they see the need. It seems more of a political than a technical nature. That's one of the potential benefits of the Galileo system: to have more than one "supplier" of such information.

Re:Jamming by whom?

[Gaima]

http://science.slashdot.org/article.pl?sid=05/08/0 8/1350218&tid=160&tid=103 [slashdot.org]

Re:Compatibility

[Wyatt Earp]

In each squad I think there is a military grade GPS reciever, since Afghanistan and more so, Iraq, more and more soldiers are carrying thier own GPS hand held which is good enough for field work.

The new military channels will be more for JDAM/Cruise Missiles and other targeting systems.

Re:Jamming by whom?

[AKAImBatman]

As I understand, one of the jamming related problems with GPS is not by criminals/terrorists, but by the government when they see the need.

No, it's more complex than that. Yes, the government can fine tune the results to cause problems for enemies, and even turn off the unencrypted civilian bands if they so choose. However, real methods exist [wikipedia.org] for sending confusing signals that will effectively jam a GPS signal. This jamming can force so called "smart bombs" to rely on internal guidance instead of GPS. The result (hopefully) is that the less precise guidance would cause the bomb or missile to miss the target.

In practical terms, it seems a bit harder than that to prevent US munitions from reaching their targets. Our guidance computers were well developed prior to the general use of GPS coordinates, and we have the capability to manually deliver ordinance wherever it may be needed. So in the end, this is about keeping the efficiency of our weapons in good order so that we have to risk fewer lives in missed targets and strafing runs.

Re:You Will Be Assimilated!

[jurt1235]

Depending on the rocket which launches the satellite, there will be a general base for the satellite to be build on. You need to be able to mount the satellite on the rocket. Total reuse of the framedesign will save a significant amount of money, so there will be attempts to reuse the frame, solar panels, and general control systems. This ofcourse if the power signature of the new equipment matches with what the frame can deliver.

One thing is a bit weird though about the first photo. Usually these satellites are assembled in clean rooms with people wearing all kinds of protection against static electricity build up and anti dust covers. So I wonder if the satellite in this picture is just a mockup to make a testfit of the equipment (never trust the drawings).

Re:You Will Be Assimilated!

[lbmouse]

Looks like a device for something out of a Dr. Seuss book. Anywho :), here are some specs [lockheedmartin.com].

Re:You Will Be Assimilated!

[AKAImBatman]

OT... something I've been wondering about, with regard to long-range communication with satellites: we know how to do networks now, why aren't we peppering space with small node probes that travel away from Earth

1. Nanoprobes wouldn't have a large enough transceiver dish.
2. We are. Have you heard of the NASA Deep Space Network [wikipedia.org]? Every sat and probe we launch becomes part of NASA's network in space. That's why when they had communications problems with the Mars Rover, they were able to send reset commands from a probe heading elsewhere. As long as they can find a number of sats with the necessary line of sight, NASA can communicate with any probe, anywhere. Even if it's on the other side of the Sun. :-)

(No, I am not privy to the exact locations of anything. So take this with a grain of salt. We have a lot of hardware up there, but space is a big place.)

Re:which #

[Ossifer]

From TFA:

GPS 2R-M1 will assume the Plane C, Slot 4 position, taking over for the GPS 2A-20 craft launched in May 1993.

Re:Jamming by whom?

[w42w42]

I remember watching a press conference with a military general at the opening of the last gulf war. The press was all lathered up about reports that Iraq was jamming GPS signals - it was assumed the Russians had given them the equipment - and the general commented that whoever was running that equipment had the worst job with the shortest life expectancy in the world at that time. Like you alluded to, any military equipment that relies on an outgoing radio signal instantly becomes a big bright target.

I see jamming in action regularly

[RebornData]

I use a laptop-integrated GPS in my car, and I drive by the Pentagon regularly for work. The GPS goes nuts on certain roads that pass near the building... the "position" of the vehicle jumps all over the place. Same thing happens near the capitol building. No suprise of course...

-R

Re:How do you compete with vaporware (Galileo)?

[Anonymous Coward]

Having worked on the Galileo internal operating software, i can say operation in 2008 is somewhat optimistic.

Re:You Will Be Assimilated!

[josecanuc]

Speaking of which, I am wondering what the heck those things on the antenna array are.

Those *are* the antennas. See the spiral bits on both kinds? That's a conductive strip. It's a helical antenna -- common on satellites. The body that looks like the main bulk is just to give the thin metal something to hold shape.

Re:which #

[Hrdina]

Actually, it will appear as PRN (pseudo-random noise) #17 on receiving equipment. That PRN is currently unused. The current vehicle in slot C4 is PRN07, and it will keep that PRN assignment until it is decommissioned by the USAF.

Re:You Will Be Assimilated!

[ChrisA90278]

You've been reading to much science fiction. Yes there are some cases where spacecraft use inderect means of communication through a relay but this is not done ad-hoc using some general purpose capability built into every spacecraft. In every case wherwe relay is used the capabilty is plaanned from the beginning. The idea of selecting some random spacecraft to use as a relay to soe other random spacecraft just can't work. The orbiters currently on mars were design specifically to relay. Closer to Earth TDRSS acts as a relay between low Earth orbit and the ground. Notice (1) that TDRSS is the relay, thaey are NOT sending data between randon spacecraft and (2) the data are passed only between LEO and the ground, not through out the solar system or even to geosync. orbit. http://msp.gsfc.nasa.gov/tdrss/oview.html [nasa.gov]

Re:Jamming by whom?

[nsayer]

any military equipment that relies on an outgoing radio signal instantly becomes a big bright target.

Yup [navy.mil].

And I rather suspect that HARMs are not limited to air defense radar systems...

Re:You Will Be Assimilated!

[LandKurt]

Have you heard of the NASA Deep Space Network? Every sat and probe we launch becomes part of NASA's network in space. That's why when they had communications problems with the Mars Rover, they were able to send reset commands from a probe heading elsewhere.

Did you even read the Wikipedia article you linked to? The Deep Space Network is an earth based network of large radio dishes that listen to deep space probes. It's not located in deep space. It's almost always easier to talk to a distant probe with a huge dish on earth than to try and use the small dish on another probe.

The closest thing to what you're discussing is NASA's TDRS system. That relays signals from earth orbiting satellites to the ground.

We need more GPS satellites

[Animats]

We've recently been struggling with a Novatel GPS that receives Omnistar High Precision corrections, and supposedly provides 15cm accuracy. The problem is that it needs to see at least five GPS satellites for Omnistar HP to work. Regular GPS requires only four, but the ionospheric corrections for Omnistar require some redundancy. Five sats are the minimum; six are better.

Unless you're in a very flat area, in the air, or on an ocean, you won't see five or six sats 100% of the time. 70-80% is more like it. If one of the sats is down (which happens; PRN #5, plane B, slot 4, wss down for 8 days recently [uscg.gov]), the outages are longer.

GPS uses six rings of four satellites each, with all rings in polar orbit. The four satellites in each ring are 90 degrees apart. So, when a satellite in a ring is near the zenith, it's usually the only one visible in that ring. The original design called for more satellites per ring; with six per ring, you'd always have at least two satellites visible per ring, as long as you could see to within 30 degrees of the horizon. But there was a budget cut in the early days of GPS.

Re:You Will Be Assimilated!

[GileadGreene]

What you say is true. In particular, the "hot new" rad-hardened processor is the RAD750, a hardened PowerPC 750. And yet...

• When the GPSIIR-M started the design process the RAD750 was nonexistent - major USAF satellites can take on the order of a decade to design and deploy.
  
• As I've said elsewhere in this thread, electronics are not necessarily that large a contributor to spacecraft mass.
  
• More capable processors may suck down more power, which tends to make other parts of your spacecarft (e.g. the solar arrays) larger.
  
• Li-Ion batteries are still considered relatively unproven in a spacecraft context. They've only been used on a few missions, and the performance and lifetime data we have on them is limited. They are unlikely to be selected for a critical system like GPS at this point.
  
• Li-Ion batteries were speculative "future technology" at the time the IIR-M was being designed. I'm pretty certain they aren't being used in the next-gen GPSIIF satellites. I'd be surprised if they made it into the GPSIII (which isn't due to deploy for another 6-8 years).
  
• Arcjets and other forms of electric propulsion have indeed proved themselves. They are in regular use on GEO comm satellites. However, whether or not EP makes sense for a given mission depends on many things. One key issue is solar array size. Using EP for an orbit transfer makes sense on a GEO comm bird because they have huge solar arrays that won't be used during the transfer - that spare power can be used to run an ion engine. In the case of GPS it's not clear that the arrays are large enough that you wouldn't need to add extra array area just to support an EP transfer - you'd end up saving propellant but making a more massive spacecraft. EP for stationkeeping is another question. But again, there are many tardeoffs involved.
  
• Satellite structures are still mostly made from aerospace-grade aluminum. There's been some work on using composites, but there are issues with outgassing in a vacuum environment, and ease of manufacture.
  
• There's been little in the way of advancements in spacecraft thermal control technology in the past couple of decades.
  
• Spacecraft antenna and RF technology hasn't changed a whole lot. Especially for precision applications like navigation signalling. Where it has changed, it's been used to add more capability rather than lower mass.
  
• Solar array technology has advanced quite a bit. But again, that just provides scope for higher-power applications (greater comm bandwidth, more processing power).
  

None of this means that the IIR-M couldn't be smaller and lighter (I personally believe it could be). But doing so requires careful design and assessment of the tradeoffs involved. Just throwing technology at the problem is not the answer. In fact, it's often the cause of the massive cost and schedule overruns that happne in DoD space programs.

Re:Russians using GPS

[ran-o-matic]

GLONASS is a GPS (global positioning system), so Aviation Week is right. One of the first examples of Russian GPS-guided bombs is the KAB-500S-E [kanwa.com] with a 1500 lb device also available.

Re:How do you compete with vaporware (Galileo)?

[aperezbios]

Wrong. Do your homework before you make idiotic claims such as "Galileo will not be fre"

From the Galileo Wikipedia Article: (http://en.wikipedia.org/wiki/GALILEO_positioning_ system [wikipedia.org])

"An encrypted higher bandwidth Commercial Service with improved accuracy will be available at an extra cost, while the base Open Service will be freely available to anyone with Galileo compatible receiver."