NASA HDEV Experiment Embraces Innovative Approach to Space Science

This block diagram shows the signal flow for the HDEV cameras on the International Space Station.

Through the new High Definition Earth Viewing experiment, the International Space Station is offering viewers on Earth a new live video feed of images captured on multiple cameras. Four high-definition cameras by Hitachi, Sony, Panasonic and Toshiba have been attached to the outside of the ISS to capture stunning video of Earth from the station’s low-orbit position, approximately 250 miles above the ground. This video is encoded and transmitted to Earth for live streaming on

NASA has a long history of working with small businesses and entrepreneurial companies on a wide range of products, and the agency dedicates significant funds toward innovative research and technology projects produced by such parties. The HDEV experiment reflects this commitment, as it was made possible by the work of entrepreneurial companies, the contributions of students in the High Schools United with NASA to Create Hardware program, and the high performance and low cost of commercial off-the-shelf cameras and video processing systems, including Visionary Solutions’ AVN443 encoder.

Numerous systems on board the ISS, including every camera used for astronaut photography, in-flight media interviews, engineering photo documentation, and other imagery needs, are COTS items and always have been. Numerous hardware projects, both on the ISS and other NASA projects, take advantage of COTS items whenever they are a feasible solution. This approach for the HDEV experiment enabled relatively rapid development — a matter of months — by engineers at the Johnson Space Center in Houston, Texas, and students in the HUNCH program who helped to design some of the camera components.

NASA HDEV4 instrument package prior to flight

The resulting HDEV experiment incorporates COTS cameras, encoding systems, command and data handling (C&DH) avionics (Ethernet), and a power data distribution box within a single pressurized and temperature-controlled enclosure.

On April 18, 2014, the HDEV enclosure and other technological experiments were hauled from Cape Canaveral to the ISS by the SpaceX unmanned Dragon commercial cargo craft, powered by the company’s new Falcon 9 v1.1 rocket. A couple of weeks later, the space station’s 12-foot-tall, two-armed Dextre robot was used to move the HDEV housing to a mounting plate on the External Payload Facility of the European Columbus lab module.

The HDEV housing was connected up to the underside of the ISS so that the enclosed Hitachi camera points forward, Sony and Panasonic cameras face aft, and Toshiba camera points nadir, or down toward Earth. Video is captured by these cameras sequentially in a looping cycle, with video from the active camera being compressed by Visionary Solutions’ AVN443 encoder into an Ethernet-compatible IP format and delivered to the ISS Columbus module via an Ethernet link.

Use of such a bandwidth-efficient encoding solution helps to make it cost-effective to produce and deliver a high-quality IP video stream from space. For this reason, NASA has employed the system already on multiple internal views. Today, for the HDEV experiment, the combination of Visionary Solutions’ H.264 hardware compression with optimized transmission technology enables beaming of a full-frame-rate HD video stream of Earth to Earth for subsequent streaming to virtually any Internet-connected device, anywhere.

When the ISS is in a position to capture video of a slowly rotating Earth illuminated by the sun, the live images delivered by the HDEV for public viewing are simply gorgeous. Although this has been an enormously popular result of the HDEV experiment, the primary goal of the project is to gather data on the effects of the space environment — especially cosmic radiation — on both equipment and video quality. With this understanding, NASA will be empowered to make informed decisions about equipment investment for future missions.

Actual exposure to the harsh rigors of space represents the best test of COTS equipment. Still, before launch, NASA performed intensive testing of each system before incorporating it into the HDEV experiment. For example, prior to building the Visionary Systems AVN443 encoder into the HDEV housing, the agency evaluated a number of encoding systems extensively to test factors such as RF emissions and performance in the presence of extreme radiation.

The view from the ISS's HDEV camera package

Using a lab at the Indiana University Cyclotron facility, NASA emulated the effect of space radiation on each encoder by applying an increasingly powerful photo beam to the unit. Ultimately, the beam applied was increased to 250 rads, which is effectively the exposure equivalent to spending four years in space. In the end, only the AVN443 encoder was able to survive radiation up to 250 rads and continue to self-recover.

In addition to maintaining exceptional performance in high-radiation environments, the encoder has power consumption of fewer than 5 Watts and efficient heat dissipation that, along with a weight of just 220 grams (8 ounces), are particularly valuable in avionics and aerospace applications. Compared with the lightest and most energy-efficient encoding solutions on the market, the AVN443 is more than 50 percent lighter and uses 50 percent less energy.

High-performance COTS systems such as the AVN433 encoder are providing numerous benefits in the realm of space science, and the HDEV experiment continues NASA’s validation of an open approach in applying commodity technology to scientific exploration. For many watching live HD streams of the Earth on their computers and mobile devices, the operational and financial gains yielded by this technical achievement may register as impressive, but the striking live HD images beamed from space are nothing short of magical.

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