We are signing off for now. We appreciate all of your questions and participation. Some of us may be around to respond to questions later on.

We are the team at NASA's Johnson Space Center who designed and built the High Definition Earth Viewing (HDEV) payload for the International Space Station (ISS). First activated in April 2014, the HDEV experiment places four commercially available HD cameras on the exterior of the ISS and uses them to stream live video of Earth for viewing online. The cameras are enclosed in a temperature controlled housing and are exposed to the harsh radiation of space. Analysis of the effect of space on the video quality, over the time HDEV is operational, may help engineers decide which cameras are the best types to use on future missions. High school students helped design some of the system components, through the High Schools United with NASA to Create Hardware (HUNCH) program.

See the current live stream here:

HDEV's Journey to the ISS:

Interview with Lead Engineer Lori Motes on Mar 7, 2014 prior to launch:

Recent interview with NASA project manager Dave Hornyak:

Team members on hand for today's AMA:

  • Dave Hornyak - NASA Project Manager
  • Lori Motes - HDEV Project Manager
  • Susan Runco - Co-Principal Investigator, Science Operations
  • Carlos Fontanot - Co-Principal Investigator, ISS Imagery Manager
  • Chris Getteau - Space Station Imagery Integrator
  • Chuck Claunch - Software Lead
  • Jeff Wheeler - Broadcast Engineer

Proof: http://imgur.com/a/oJoh8
Group Photo posted

Comments: 91 • Responses: 23  • Date: 

liamkennedy9 karma

Hello HDEV Team! (Liam here - ISS-Above )

Of course as you know I just can't thank you enough for what you have provided to the world with this capability from the ISS.

Now my question.

What was your biggest surprise or unexpected result from launching this experiment?

HDEV_Team4 karma

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.

phonedesk4 karma

Love the HDEV! I leave it on every day and have a folder full of cool screenshots.

Do you guys expect to continue the feed beyond the stated end date later this year provided the cameras are still working well?

HDEV_Team3 karma

Currently HDEV has been extended to 2017. Another payload is scheduled to take our place at that time.

D3imos3 karma

is there a big difference between a camera used on earth and a camera used in space?

HDEV_Team4 karma

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.

parall4x3 karma

As a part of this study, will you be quantitatively or qualitatively comparing the degradation of video quality over time? If quantitatively, what metric will you use to measure this? Will measurements be observed through a software process?

HDEV_Team9 karma

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.

phonedesk1 karma

Is this why the cameras are sometimes not rotating?

HDEV_Team2 karma

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

BradleyWill_I_am3 karma

How does the signal travel from the camera get back to Earth? (What kind of radio signal can travel that far?) Is there a delay and if so, for how long?

HDEV_Team4 karma

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.

phonedesk2 karma

how delayed is it by the time we see it?

HDEV_Team3 karma

HDEV video is delayed by about 20 seconds to the end user.

scknarr2 karma

Hindsight being 20/20, is there anything you wish you had done differently when designing and implementing the HDEV payload?

HDEV_Team5 karma

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.

TonySwank2 karma

Do you have a favorite picture taken from HDEV?

From HDEV's perspective, could you rank the continents in order of attractiveness?

HDEV_Team3 karma

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.

isktaine2 karma

Sometimes the cameras can't be streamed because of lack of signal, does this always happen at the same point? (e.g. Is it when the ISS is over a certain part of the earth where it is far from any transmitters?) Or is it dependent on other factors, e.g. weather?

HDEV_Team3 karma

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.

FanOfFlan2 karma

Firstly I'd like to say what a cool idea this is. It makes it so much more enjoyable knowing it's live footage. I have a billion questions but i'll ask just a few.

Firstly how much of a delay in the footage is there?

what type of camera/hardware are you using for this?

and what are you plans for the future? will this keep going? multiple camera angles?

HDEV_Team8 karma

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.

guzzling2 karma

What would be the next step in this experiment?

HDEV_Team2 karma

The next step is to analyze the camera performance and make recommendations for future use in space.

signuptopostthis2 karma

  1. Can the cameras move?
  2. What is the amount of delay observed in the live stream?

I want to thank you guys for this. When I am feeling down or just having a bad day, I go to the live stream and just watch our beautiful earth spin. Damn yes we may be small, yes we may be just a speck of dust in the vast expanse of the universe, but what defines us humans are not those things. Its the pursuit of science despite those things. Thanks for being the frontier of human knowledge.

HDEV_Team1 karma

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.

MadRockSci1 karma

Detailed engineering Q's. What is the window material? (Fused silica?) Does it have broadband AR coating inside and out? Is the internal environment 1 atmosphere N2?

HDEV_Team2 karma

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.

guzzling1 karma

will we be able to see "cities" and lights during night anytime soon?

HDEV_Team6 karma

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.

texantiff1 karma

Which components were the high school students from HUNCH involved in designing, and how did you work with them? Was it in person in labs, or virtually?

HDEV_Team2 karma

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.

poweruser821 karma

Do you receive the stream of the 4 cameras in each moment or do you have to choose one? How much bandwidth are you allowed to use for downstream? What resolution have the image you receive?

Thanks for the emotions HDEV gives to earthlings

HDEV_Team3 karma

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.

cussbunny1 karma

If something were to happen to the camera, would the ISS crew be able to service it, or would that be the end of the experiment?

HDEV_Team2 karma

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.

poweruser821 karma

Is there a reason that nadir cam doesn't point exactly to nadir but its FOV is slightly shifted toward East? See http://www.satflare.com/track.asp?q=25544#TimeBar for reference.

HDEV_Team3 karma

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.

familykins1 karma

Have radiation hits been a problem?

HDEV_Team2 karma

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

liamkennedy1 karma

If you were to have an opportunity to build the next version of HDEV – what new capabilities would you put highest on the priority list?

HDEV_Team2 karma

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.

Radiowolf1 karma

In what manner will the lessons learned from HDEV be applied to future imagery gathering procedures? Have you determined any factors as of yet, related to camera construction or technology that produce better image quality or sensor longevity? Furthermore, does the fact that each camera has a distinctly different FOV make it more difficult to interpret certain data?

HDEV_Team1 karma

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.

Xasos1 karma

What do you do in terms of compression for the live video? And is there any reason why 720p is the highest resolution?

HDEV_Team1 karma

The video is compressed to 6Mbps. We chose 720p because that is the NASA standard for video distribution.