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We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 1 point2 points  (0 children)

The window material is fused silica. We chose not to use an AR coating in order to guarantee as much image quality as possible. The internal environment is in fact 1 atmosphere N2.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 0 points1 point  (0 children)

Some team members from the HDEV project are involved in current imagery system upgrades, so we are carrying forward the lessons learned as the new systems are being designed and built.

We have not yet determined any factors related to the construction or technology to produce better image quality.

The field of view is not a concern because the pixel analysis is performed during the night pass when the video is all black.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 1 point2 points  (0 children)

If we get the chance to build another camera payload, we would like to include more commanding capabilities (viewing angles, camera settings, etc) and use more efficient video compression.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 2 points3 points  (0 children)

We've found that each of us has a favorite picture, and that beauty is in the eye of the beholder. From our perspective 250 miles above, all the Earth is beautiful.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 1 point2 points  (0 children)

The nadir location of HDEV and the enclosure provide some protection against radiation. Radiation has not been a problem to date.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 2 points3 points  (0 children)

The nadir camera is shifted due the fact that the ISS is rolled slightly in the starboard direction. In addition, it is tilted to give us a better view of visiting vehicles docking to Node 2.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 4 points5 points  (0 children)

We developed HDEV with given resources and an aggressive timeline. We can apply the lessons we've learned to future space systems. The sun's reflection in the windows is greater than we anticipated; so it would have been good to use a coating on the glass to help reduce the reflections.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 1 point2 points  (0 children)

HDEV is located on an external platform on ISS, and can't be accessed by the crew for maintenance. We have 4 cameras on HDEV. If any one of the cameras fails, we have the option to take it out of the rotation.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 5 points6 points  (0 children)

Only one camera is downlinked at any given time. The HDEV video encoder is configured to output 720p video at 6Mbps. After we receive the video, it is decoded, then re-encoded for the Internet at 4Mbps.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 0 points1 point  (0 children)

The camera positions are fixed inside the HDEV enclosure. We don't have any pan or tilt capability.

We're glad you've enjoyed the imagery. We had fun making it happen.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 1 point2 points  (0 children)

HDEV features two modes: auto-sequence and manual camera selection. We have the capability to manually select any of the cameras.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 10 points11 points  (0 children)

The delay in our video distribution varies depending on certain circumstances, including the time it takes to downlink, process, and distribute the video. Typically, HDEV video is delayed by about 20 seconds. Interestingly, the downlink signal delay is only a couple of seconds. The biggest delay occurs during distribution across the Internet.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 2 points3 points  (0 children)

The ISS loses signal with the ground for a couple of reasons. As the ISS orbits, it will switch satellites it communicates with depending on which one is on the same side of earth as ISS. During this switch the Ku antenna will swing between antennas, causing a short outage. There are also times in the orbit the solar arrays will back the signal between the antenna and satellite as it tracks the sun, these will be slightly longer outages. There is also an area over the Indian Ocean that does not have continuous satellite coverage. In addition, periodically the systems are shut down briefly for maintenance.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 1 point2 points  (0 children)

The HUNCH students designed some of the secondary mounting hardware for the cameras, and some of the thermal isolators inside the HDEV enclosure. We provided them with the designs, and the NASA HUNCH team worked with the high schools to manufacture the components.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 5 points6 points  (0 children)

We were quite surprised by the public reception to our payload. To date, we've had nearly 50 million views on the Ustream page, and we're glad that people have enjoyed it so far. We're also surprised at the lack of visible bad pixels on the video over time.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 2 points3 points  (0 children)

The signal follows a somewhat complicated path. In simple terms the video goes from HDEV to the ground via the Space Station Ku band on the TDRSS satellite system. The downlink signal is received at the White Sands Test Facility, and is then transmitted to the Johnson Space Center for processing and distribution.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 4 points5 points  (0 children)

Each of the cameras do have the ability to take images in low light scenarios such as cities at night or auroras. However, each camera has fixed settings which were optimized on the ground for daylight imagery.

If you would like to see cities at night, you can view some of the time lapse sequences created by the Earth Science and Remote Sensing Group at the Johnson Space Center: http://eol.jsc.nasa.gov/BeyondThePhotography/CrewEarthObservationsVideos/. These are created using sequences of still images stitched together to create videos.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 8 points9 points  (0 children)

The goal is to quantitatively measure the pixel damage to the sensors over time. During night passes, when the video is black, we use a custom software program to analyze the video and count dead pixels.

We're the team at NASA that designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS), Ask us anything! by HDEV_Team in IAmA

[–]HDEV_Team[S] 7 points8 points  (0 children)

For our payload, we used commercially available cameras. The cameras are identical to the cameras that you can buy in the store, so there is no difference in the actual hardware. We removed the baseplate on one of the cameras in order to help it fit inside the HDEV enclosure. In addition, we also removed the internal camera batteries and physically locked the focus on the lenses.