NASA Takes Streaming Into Space
But first things first. Since NASA is tax-supported, public outreach is paramount, Hames believes. "One of the biggest things we can do for the public is to send down pictures and video. That gets the public engaged more than just about anything." And when it comes to video, people want more of it, and in better quality, Hames says. The general public has higher expectations for video quality than ever before. "We need to find a way to get better video down from these explorations to keep people excited, make them feel like part of the process, feel like they are really there," says Hames, who is looking even further ahead. "I think everyone sees the writing on the wall," he says. "When we go back to the moon, we want to be high definition or better."
Still in Experimental Phase
Hames explains that the Space Video Gateway is something which is known in NASA-speak as a Detailed Test Objective (DTO). "We call these things DTOs," says Hames. "It's basically an experiment in space. We're trying to find out if this thing makes sense to go into the full-blown system, at which point we'd add video switchers and the whole nine yards," he says.
"The Space Station, as a whole, is limited to 150Mbps per second," Hames explains. "And right now we are living well within that margin, but we're getting ready to launch the extra modules that the European Space Agency and the Japanese Aerospace Exploration Agency are building for us. And so the more users we get up there, the more bandwidth we'll need. And we're going to start to feel a bandwidth crunch maybe in the next couple of years." The bottom line is that the efficiency of the Space Video Gateway will allow NASA to collect and distribute more video, according to Hames.
And, of course, the higher-quality high-def video will also be a boon. It will also be something new, says Hames. "You couldn't pump the hi-def video through the station’s existing video system. It is just not compatible with it. It only understands NTSC." So a big advantage the SVG will provide over the Space Station's old video system is its high definition capability. Hames says that he and his colleagues have recently run a number of tests of the SVG that have been very positive. "Right now we're we running the high-def at about 30 Megabits per second and it looks really good. The NHK people consider it broadcast quality, sufficient quality to send out to Japanese homes."
What Is the Space Video Gateway?
Despite its fancy moniker and important function, the Space Video Gateway is little more than a rack-mountable server--a CS-900 from Crystal Group--according to Hames. "It is a Windows 2003 server box, and it has a bunch of video encoding and IP packetizing cards in it," he says. It has two operational modes—high definition and standard definition. "For the high definition we're using the LSI Logic HDTVxpress card and DVB Master. The LSI card does MPEG-2 encoding, while the DVB Master does the IP packetizing. For standard definition we're using a Digital Rapids encoding card and that comes with the software MPEG encoding and we do software IP packetization on the computer."
Hames explains the route the video takes after collection, compression, and packetization at the Space Station: "Those IP packets are sent to a special card that [NASA] built called the Orbiter Communications Adapter. We first built it for the shuttle back in 1994 and have been flying it ever since. What that does is it takes the IP packets and converts them into the NASA-proprietary SATCOM protocol for the TDRSS (Tracking and Data Relay Satellite System). We've had these satellites up for a long time now. Near as I can tell, we were running IP over satellite before just about anybody, definitely before the commercial people," says Hames. "Well, we have our own satellite system, and so we can do stuff like that," he adds.
The video goes from the Space Station to a TDRSS satellite to NASA's ground station at the White Sands Complex in Las Cruces, New Mexico. "And then they actually put a second IP wrapper around it," says Hames. "And that's just because all the data that comes from the Space Station, whether it's IP or not, gets that second IP wrapper." From there, it goes by land line to Johnson Space Center in Houston, the Marshall Spaceflight Center in Huntsville, Alabama, and other NASA centers. "When it gets to our center Houston, we reverse the whole process so that the video is available for viewing," says Hames.
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