spacer
 
Advanced Search
Astrobiology Magazine Facebook  Astrobiology Magazine Twitter
  
Expeditions Diaries Expedition 31: Letters to Earth Earth Photography: It's Harder Than It Looks
Earth Photography: It's Harder Than It Looks
Source: NASA Blogs
print PDF
Missions
Posted:   09/24/12

Summary: In this installment of his diaries from the Expedition 31 crew, astronaut Don Pettit talks about the difficulties of photographing Earth from orbit. Viewing our planet from above provides important information about our planet, including the effects of climate change on the land and oceans.

Jelly on Both Sides
Feb 17, 2012 04:06:38 PM


Dinner time for Don Pettit on the International Space Station. Credit: NASA
When your slice of bread falls on the floor, everyone anxiously looks to see if it landed jelly side up or jelly side down. Simple probability gives a 50-50 chance either way, but it seems more correlated to the difficulty of cleaning that particular section of flooring.

On space station the probabilities are still the same, but the results are different. I fumbled my bread after spreading a generous layer of my favorite concoction, peanut butter and honey. It sped toward the overhead panel and hit it before I could intervene. Fortunately, it landed jelly side out (it’s interesting how many figures of speech have gravity-oriented references), so the 50-50 odds were in my favor this time.

Unfortunately, it ricocheted and sped off in a different direction. I noticed that the angle of incidence equaled the angle of reflection. My earth-honed intuition anticipated a different motion, so I was not able to keep up with the errant slice. Like a real-life version of the game “asteroids,” it went on to hit a second panel. Jelly side was out again, so the 50-50 statistics were still in my favor. One more time my hand was lagging the trajectory. Like failing to flip heads three times in a row, the third collision was jelly side in, which immediately halted all motion. And just like on Earth, the outcome seemed related to the difficulty of cleaning the landing zone. After having hit two easy-to-clean aluminum panels, it landed on a white fabric covering on a patch of Velcro pile.

The fatalist in me accepts the inevitable Zero-G result of landing jelly side “down,” so I decided to make sure the probability would always be 100%. Realizing that the bread is merely a vehicle for conveying peanut butter and honey, I decided to spread it on both sides. In weightlessness, it’s easy to balance your slice on its edge so that it can be parked on the galley table without any fuss. And the result is pure tastebud heaven. I do it this way because I am in space, and I can.

Earth Photography: It’s Harder Than It Looks
Feb 24, 2012 04:25:16 PM


From my orbital perspective, I am sitting still and Earth is moving. I sit above the grandest of all globes spinning below my feet, and watch the world speed by at an amazing eight kilometers per second (288 miles per minute, or 17,300 miles per hour).

The Aurora of Earth as photographed from the International Space Station. Credit: NASA / Don Pettit
This makes Earth photography complicated.

Even with a shutter speed of 1/1000th of a second, eight meters (26 feet) of motion occurs during the exposure. Our 400-millimeter telephoto lens has a resolution of less than three meters on the ground. Simply pointing at a target and squeezing the shutter always yields a less-than-perfect image, and precise manual tracking must be done to capture truly sharp pictures. It usually takes a new space station crewmember a month of on-orbit practice to use the full capability of this telephoto lens.

Another surprisingly difficult aspect of Earth photography is capturing a specific target. If I want to take a picture of Silverton, Oregon, my hometown, I have about 10 to 15 seconds of prime nadir (the point directly below us) viewing time to take the picture. If the image is taken off the nadir, a distorted, squashed projection is obtained. If I float up to the window and see my target, it’s too late to take a picture. If the camera has the wrong lens, the memory card is full, the battery depleted, or the camera is on some non-standard setting enabled by its myriad buttons and knobs, the opportunity will be over by the time the situation is corrected. And some targets like my hometown, sitting in the middle of farmland, are low-contrast and difficult to find. If more than a few seconds are needed to spot the target, again the moment is lost. All of us have missed the chance to take that “good one.” Fortunately, when in orbit, what goes around comes around, and in a few days there will be another chance.

It takes 90 minutes to circle the Earth, with about 60 minutes in daylight and 30 minutes in darkness. The globe is equally divided into day and night by the shadow line, but being 400 kilometers up, we travel a significant distance over the nighttime earth while the station remains in full sunlight. During those times, as viewed from Earth, we are brightly lit against a dark sky. This is a special period that makes it possible for people on the ground to observe space station pass overhead as a large, bright, moving point of light. This condition lasts for only about seven minutes; after that we are still overhead, but are unlit and so cannot be readily observed.

Ironically, when earthlings can see us, we cannot see them. The glare from the full sun effectively turns our windows into mirrors that return our own ghostly reflection. This often plays out when friends want to flash space station from the ground as it travels overhead. They shine green lasers, xenon strobes, and halogen spotlights at us as we sprint across the sky. These well-wishers don’t know that we cannot see a thing during this time. The best time to try this is during a dark pass when orbital calculations show that we are passing overhead. This becomes complicated when highly collimated light from lasers are used, since the beam diameter at our orbital distance is about one kilometer, and this spot has to be tracking us while in the dark. And of course we have to be looking. As often happens, technical details complicate what seems like a simple observation. So far, all attempts at flashing the space station have failed.

Our Fancy Coffee Machine
Feb 29, 2012 01:03:17 PM


Water is essential for life as we know it... including the astronauts on the International Space Station. Credit: Don Pettit / NASA
During the flight of STS-126 in 2008, we carried up three refrigerator-sized pieces of equipment. One was a toilet for the NASA side of space station. There was already one on the Russian side, so this one gave us redundancy. In the past, when the toilet broke, all work had halted until we fixed it. No other single piece of equipment fell into this category of importance. The oxygen generator could break, and maybe in a day or two we would fix it; same with the carbon dioxide scrubber. But when the toilet broke—now that was serious.

The second piece of equipment we carried up was a small chemical plant. It contained a distillation apparatus, catalytic reactors, pumps, filters, and plumbing. It was a chemical engineer’s dream. The liquid effluent from the toilet was plumbed to the inlet of this machine.

The third piece of equipment was a new galley. It sported an injection port for filling our drink bags and rehydrating freeze-dried food with our choice of hot or room-temperature water. It also had a hot box for warming thermally stabilized meat pouches (canned meat without the can) and a small refrigerator—not for science samples, but for the crew’s food. The inlet to the galley was plumbed into the outlet of the chemical plant. This completed what we call our regenerative life support system. Simply put, what goes out one end is processed, reworked, and put back in the other end.

Astronaut Don Pettit onboard the International Space Station with his collection of cameras used to photograph the Earth from above. Credit: NASA
Water is an essential ingredient not just for us, but for all life forms that we recognize. And water is always in short supply on a spacecraft. There may be water shortages in some places on Earth, but spaceflight redefines the meaning of the word “desert.” Closing the water loop will therefore be essential technology when humans venture away from Earth for long periods of time. If the toilet fails on a mission to Mars, the crew will run out of water and die. Earth orbit, where spare parts and engineering knowledge are close by, is the ideal place to refine this technology and produce equipment that is truly robust. I call this engineering research; it is complementary to scientific research, and is one of the more important activities that we conduct on space station.

Nowhere on Earth do we recycle urine using portable machinery. Not in Antarctica, not on ships at sea, not in our driest deserts. We choose to let Earth do the recycling, not a machine. Our recycling system on space station is not a one-time demonstration, nor a test of astronauts’ ability to handle the “yuck factor.” It’s a day-in, day-out operation, designed as an integral part of the overall spacecraft water balance. With this technology, we are truly on the frontier, and we have serial number 001 of a complex machine. Of course it breaks down—constantly. And of course, we are always fixing it. Of course there is a steady stream of spare parts arriving from Earth. Any new technology is like this. The first crews arriving at Mars will thank us for our urine-stained hands.

Morning is a time for comfortable habits, and so it is on space station. Each morning I float out (“getting up” is obviously a gravity-centric expression) and do my daily routine. I can hear the rumbles of the chemical plant. It vibrates the deck rails and gives your feet a massage at the same time. Then I float over to the galley and make a bag of coffee. Kona is one of my favorites; I can feel the caffeine race to my brain and stimulate my thoughts. It occurs to me that our regenerative life support equipment is really just a fancy coffee machine. It makes yesterday’s coffee into today’s coffee.


Related Stories

Astrobiology Roadmap Goal 6: Life's future on Earth and beyond

The Road to Space
What Makes an Explorer?
Me and My Spacesuit
Godspeed to Earth
Grand Views for the Camera
Perpetual Twilight
The Sweet Smell of Molecules
The World Through a Looking Glass
Flying Without Wings
About Us
Contact Us
Links
Sitemap
Podcast Rss Feed
Daily News Story RSS Feed
Latest News Story RSS Feed
Learn more about RSS
Chief Editor & Executive Producer: Helen Matsos
Copyright © 2014, Astrobio.net