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Reader SurveyThe Video Horizon
Sep 1, 2007 12:00 PM, By Tom Patrick McAuliffe
NASA Television tracks America's space program with analog, digital, HD, and streaming video technologies.
"One of the things I've been using the camcorders for is to record images of lightning storms from space. While your eyes are much more sensitive than the cameras, the camcorders do a surprisingly good job with nighttime shots." —While living aboard the International Space Station, NASA Astronaut and ISS Science Officer Ed Lu wrote about his experiences using video in space.
All Photos courtesy of NASA
Look up in the sky. It's a spacecraft; it's an astronaut — it's a videographer? It's all three. As NASA continues to explore space and build the International Space Station (ISS), video is there documenting it all. And NASA Television is helping by allowing us all to watch some of our tax dollars at work 24 hours a day, seven days a week.
NASA TV was established in the early 1980s to provide the agency's Space Shuttle Program managers and engineers with realtime video of space shuttle operations and liftoff-to-landing coverage of missions. More recently, programming is also provided to the media and U.S. television networks. And while NASA TV is not a public or commercial TV station, it provides informational and educational programming on space exploration, space science, earth science, and aeronautic research that rivals that of any traditional network.
As is the case with most video operations today, the new digital and high-definition formats are making inroads while traditional analog video and newer DV/DVCAM equipment continues to be used as NASA TV pursues its mission of documentation and education.
“NASA Television exists to provide the agency with coverage of missions from human space flight to expendable launch vehicles,” says NASA TV Executive Producer Fred Brown. His team provides the news media with feeds (B-roll, soundbites, etc.), coverage of NASA news conferences, and press briefings, 3D animations to support and help explain missions, and produced videos of various programs such as the Hubble Space Telescope and Mars Rovers. NASA TV also runs educational programming produced by NASA's Education Division for schools across the country.
NASA TV is carried on numerous television cable systems around the country and on the major satellite systems. Programming is also carried on cable TV in Canada and in parts of Europe and Asia. For more than two years, it has also been available on the Internet as streaming video through NASA TV's website, www.nasa.gov/ntv. In addition to all the internal uses at the agency, NASA TV distributes three digital video channels by satellite: one for the general public, one geared toward education, and one for the media. The channels are carried by MPEG-2 digital C-band signal to two satellites (AMC 6-17C and AMC 7-18C). (If the programs are not carried by the local cable company, a digital video broadcast [DVB]-compliant integrated receiver decoder [IRD] and a satellite dish is needed for reception.)
The Broadcast Center for NASA TV is located in Washington, D.C., at NASA Headquarters (HQ). All NASA Centers (Johnson, Kennedy, Goddard, Ames, etc.) have television units that are producing live events and various video products for television. There are 10 NASA Centers, and each has its own television infrastructure that supports mission, programs, and activities at its location. All centers also provide material for use on NASA TV. The number of video specialists at each location varies, but there are more than 100 throughout the agency.
Television Master Control at Goddard Space Flight Center in Maryland.
“Content originates at the centers and is routed to NASA headquarters via the NASA wide-area network. At headquarters, the content can either be recorded for playback later or routed in realtime to be multiplexed with other content for other channels. The multiplexed signal is then routed to Goddard Space Flight Center [GSFC], where it is modulated and uplinked to a commercial satellite [currently AMC 6-17C],” says Rodney Grubbs, chair of the NASA DTV Working Group and based at the Marshall Space Flight Center in Huntsville, Ala.
The system starts with the output from a center's video production switcher. Some centers still have legacy NTSC switching; some can produce entirely in SD SDI; and now, two centers use HD SDI. Each center has at least one Harmonic 4:2:2 SD MPEG-2 encoder and another low-latency SD MPEG-2 encoder (also Harmonic).
“We typically encode at about 7.5Mbps 4:2:2 long GOP,” Grubbs says. “The video stream can be recorded to tape or routed to the multiplexer. Standard configuration is to have four channels [all MPEG-2 4:2:0 long GOP] multiplexed together.”
Channel 101 is the NASA Public Services Channel, which is the channel most people know as NASA TV; that is what's placed on cable systems and the digital satellite providers. Channel 102 is the Education Channel typically programmed with content from a playback server at headquarters. Channel 103 is the Media Services Channel, and it sometimes mirrors what is on the Public Channel, but it is also used for raw feeds to the media of live shots and video files. Channel 104 is the Space Operations Channel, which is used internally for NASA space flight operations. “Often, content from this channel is also simulcast on the media channel and public channel,” Grubbs says.
As expected, when it comes to technology, NASA and NASA TV can rival any broadcast operation in the world. In August, the STS-118 Space Shuttle Endeavor mission put even more new technology to the test. “We enabled multicast routing within the NASA wide-area network, so instead of routing video from a center just to the headquarters in D.C., we can multicast it to other NASA centers around the U.S.A.,” Grubbs says. “The centers can decode it with the same IRDs they use for satellite reception. This gives us a lot of capability within the agency for contingencies and for sharing video in realtime. We also fully tested an HD channel. The HD stream was encoded at the Kennedy Space Center [12Mbps 4:2:0 MPEG-2 long GOP] with a Harmonic HD encoder. We slightly reduced the bit rate on channel 101, reduced 102 to just a graphic suggesting folks tune to 101, and added a fifth channel, 105, which simulcasted the launch in HDTV.”
Astronaut Barbara R. Morgan, mission specialist and teacher aboard the Space Shuttle Endeavor, uses a flight model Sony DSR-PD100 DVCAM during a farewell ceremony in the Zvezda Service Module of the International Space Station before returning to Earth.
Grubbs says he expects NASA TV to continue to provide high-definition video feeds via satellite in the future. And other enhancements are also on the horizon. “Looking into the future, we're considering changing the way we modulate the aggregate multiplexed signal so we can get additional bandwidth on the C-band transponder. Right now, we're limited to about 36Mbps, and by making the change, we'd be able to add the HD channel and not reduce any of the other standard-definition channels,” he says. “Later in the decade, we're considering transitioning from C-band to Ku and from DVB to DVB-S2 with a mix of MPEG-2 and MPEG-4. That way, we could add another HD channel and get up to 70Mbps on a single transponder.”
Such a complex collection of media outlets is not without its challenges. In addition to the transition to digital and HDTV, one design gotcha with a network this large with this architecture is signal latency, according to Grubbs. “Interactive events such as internal NASA Q&A sessions with the administrator or press conferences or live shots are affected adversely with the latency of this architecture,” Grubbs says. “Doing an encode at a center, decoding at headquarters, re-encoding and multiplexing, then uplink at GSFC [Goddard Space Flight Center], with all the IP packetizing and depacketizing for routing adds up to a pretty hefty latency. To lower the latency, we put in place some encoders optimized for latency performance, encode 4:2:0, and then a ‘pass-through’ at HQ going straight into the multiplexer [with no decode/encode cycle]. This cuts the latency in half but still leaves it at slightly more than two seconds.
“The shuttle program has its own leased satellite transponder for program support. By digitizing [making the signal digital] all of the shuttle services, we'll be able to use some of the bandwidth for a direct low-latency MPEG-2 stream for live shots [Center X uplinks direct to satellite, and Station Y receives it].” Grubbs says switching all Space Shuttle satellite services to digital video feeds should be finished by the time you read this. To read about NASA TV Master Control, go to www.digitalcontentproducer.com.
With such a comprehensive distribution network, NASA's production approach is also multifaceted. More than 100 videographers at the 10 NASA Centers gather footage for both internal as well as public uses such as NASA TV. The production pipelines vary with the content and the location, but there is some commonality.
Throughout NASA, handheld HD cameras are predominantly Panasonic Varicams and, more recently, the Panasonic AJ-HDX900. The handheld SD cameras are a mix of Panasonic, Sony, and Thomson Grass Valley DV-level cameras. For flight, NASA missions use Sony DSR-PD100 DVCAM camcorders.
Johnson Space Center in Houston uses a Euphonix System 5b to feed audio to NASA TV.
“For HD, NASA is a 720p shop, so the industry standard for that format has been DVCPRO. The new AVC Intra format by Panasonic supports native 720p, and Grass Valley's new Infinity camera system can record native 720p as well,” Grubbs says. “Sony is coming out with a new variant of XDCAM, which claims to be able to record native 720p, but their format is MPEG-2 long-GOP-based, and the NASA standard for HD acquisition currently requires no GOP, so we're going to have to test that to see if we need to mod the standard. For standard def, our videographers have lots of options, but HDV is discouraged and not used for anything meant to be distributed for production or broadcast.”
New gear and formats are constantly being used and tested. Grubbs indicates his testing of Panasonic's AVC Intra codec is encouraging. “[AVC Intra] is the best native recording camcorder format we've ever had in the lab. It looks very promising, but we just got our first camera in last week and haven't taken it out into the real world yet,” he says.
The bulk of the programming is live. For postproduced shows, most NASA editors use the suite of tools they have on their computers for live sweetening (Apple Final Cut Pro or Avids are most common). Additionally, most NASA Centers have two to four video and audio postproduction workstations attached to a SAN fiber-channel network. “I think most of the Final Cut Pro folks are also using Apples' Xsans for storage,” Grubbs says. NASA videographers don't do 5.1 mixes — instead, they capture with discrete dual mono audio channels so that producers can do their own 5.1 mix later.
When it comes to live feeds for NASA TV, the video and audio is distributed from the source (usually a studio or an auditorium) through a technical control room, where the video is routed to a production switcher and the audio is routed to the audio control room. Both feeds are then combined, after inserting whatever audio delay is necessary depending on the source of the audio, back in the technical control room. The combined audio/video program is then routed to the encoder for final distribution across the NASA WAN or through the broadcast chain.
Contributing Writer and Reviewer Tom Patrick McAuliffe is a journalist and media creator who has been writing for DCP and related Penton publications for more than 12 years.
