We can measure the amount of ice melting from the ice sheet in Greenland from space by the effect that the moving mass has on gravity (GRACE mission).
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Space is getting harder to see. Earth is polluting the view with orbital junk and party lights that makes viewing futile. Like having fireworks at a Solar eclipse location. Thank heavens for interference filters! Dark skies to all.
The 2001 Mars Odyssey Orbiter was launched April 7, 2001, and arrived at Mars on October 24, 2001. It is interesting to note that the 2001 Mars Odyssey was aerobraking around Mars at about 100 km altitude, the same altitude considered Space for the $10 million Ansari X Prize won in 2004 by SpaceShipOne. On board was the THEMIS (Thermal Emission Imaging System)
There was a lively discussion on Space.com Uplink forums regarding THEMIS, but very little information available, so I decided to find some. Several well placed and cheerfully worded phone calls to JPL got me a personal return call from Mr. Greg Mehall, Systems Engineer at Arizona State University. He said, “You must know somebody important here, I got messages from half a dozen people saying ‘you’ve got to talk to this guy’”.
This also prompted an email to me from Phillip Christensen, Principle Investigator for THEMIS at ASU. He sent much of the information below, before it was available to the general public.
Mr. Mehall built the VIS camera from a Malin Space Science Systems unit. Mr. Mehall and his group are the ones who give the commands to the Odyssey spacecraft to capture the images.
The Visible Imager has a 4 MB buffer. In the along-track direction, the VIS frame size is limited by its 4 Megabyte data buffer size. The along-track dimension can be 15-65 km, depending on the number of bands used (65 km is the maximum for a single-band image). On any given swath, the VIS data must "wait" for the IR data collection to finish before being transferred to the spacecraft, since the VIS and IR share a single high-rate data interface.
Some of the interesting points:
1) The Odyssey spacecraft passes over a specific point on Mars once every 4 months.
2) The spacecraft spends 15 minutes each day taking pictures, and 23 hours 45 minutes transmitting data back to Earth.
3) The buffer in the VIS camera has a 4 megabyte capacity so it can store 19 single band images or 3 five band images.
4) The visible image camera must wait for the IR camera to transfer data to the spacecraft memory because they use the same data bus and the IR camera has priority.
5) The VIS has an overlap of 25 rows.
6) The IR camera transmits data at 4Mbps.
7) The VIS camera transmits data at 1Mbps.
8) The IR band of the VIS is very noisy and has poor resolution.
9) The THEMIS camera was since March 2001, so images will be available in Sept-Oct. after their 6 month product generation and validation period.
Greg also explained that the THEMIS VIS is not capable of taking “true color” images because it does not have the proper filters for that. However, using the violet filter with the green and a red will produce an image that is close. Technically, all images from the VIS will be false color images. The data will be available on PDS, and anyone can combine the different bands to make their own “color” images. One of the problems with some of the wording in this area is that, what may be practical in application may not be technically correct. Although no “true color” images will be available from VIS, the combined images can be manipulated to approximate a true color photo. Some color information loss will occur but it will be minimal.
The VIS camera in THEMIS is a push-broom camera. It has five filters laminated to the surface of a 1024 x 1024 CCD element. These filters are aligned consecutively in the downtrack direction. Each filter is about 200 pixels long and 1024 pixels wide. The CCD is scanned about once every second, which is the time it takes for the Odyssey to move almost the width of a filter. Therefore, each filter is scanned just before it has crossed over into new territory. There is a 25 pixel row overlap, and this overlap is used to help align successive images together. The result is that the camera can obtain continuous images on each of the five filters at the same time. The only limitation to downtrack image length is the available memory.
The Visible Image Camera in THEMIS has filters in 5 visible bands, well, not quite.
The bands are:
1---- 0.870µm INFRARED
4---- 0.751µm RED - 780-622
3---- 0.652µm RED - 780-622
xxxxx---- no filter orange - 622-597
xxxxx---- no filter yellow - 597–577
5---- 0.553µm GREEN - 577-492
xxxxx---- no filter blue - 492-455
2---- 0.423µm VIOLET - 455-390
Notice that only four of the filters are in the visible range and one is in infrared. Also notice that there is no blue filter which is needed to make “true” color, RGB.
So what color is an image if it is not true color? It depends on your definition of true color. When most people say true color, they mean an image as it would appear to the human eye under normal lighting conditions. However, it could be said that an image taken through a 0.553µm Green filter and then reproduced with that same wavelength color is true color. It will be “green and white”, but it will be the same green that the filter allowed through when the image was taken. This can be very misleading, because when equivalent amounts of red and blue are added from corresponding exposures taken through the appropriate red and blue filters, the resulting photo may not contain any green at all. You can prove this to yourself by taking photos through various filters with your own camera.
All other pictures taken with the THEMIS camera are monochromic. Because they are exposed in infrared, all viewable images from infrared will be in false color.
There was a lively discussion on Space.com Uplink forums regarding THEMIS, but very little information available, so I decided to find some. Several well placed and cheerfully worded phone calls to JPL got me a personal return call from Mr. Greg Mehall, Systems Engineer at Arizona State University. He said, “You must know somebody important here, I got messages from half a dozen people saying ‘you’ve got to talk to this guy’”.
This also prompted an email to me from Phillip Christensen, Principle Investigator for THEMIS at ASU. He sent much of the information below, before it was available to the general public.
Mr. Mehall built the VIS camera from a Malin Space Science Systems unit. Mr. Mehall and his group are the ones who give the commands to the Odyssey spacecraft to capture the images.
The Visible Imager has a 4 MB buffer. In the along-track direction, the VIS frame size is limited by its 4 Megabyte data buffer size. The along-track dimension can be 15-65 km, depending on the number of bands used (65 km is the maximum for a single-band image). On any given swath, the VIS data must "wait" for the IR data collection to finish before being transferred to the spacecraft, since the VIS and IR share a single high-rate data interface.
Some of the interesting points:
1) The Odyssey spacecraft passes over a specific point on Mars once every 4 months.
2) The spacecraft spends 15 minutes each day taking pictures, and 23 hours 45 minutes transmitting data back to Earth.
3) The buffer in the VIS camera has a 4 megabyte capacity so it can store 19 single band images or 3 five band images.
4) The visible image camera must wait for the IR camera to transfer data to the spacecraft memory because they use the same data bus and the IR camera has priority.
5) The VIS has an overlap of 25 rows.
6) The IR camera transmits data at 4Mbps.
7) The VIS camera transmits data at 1Mbps.
8) The IR band of the VIS is very noisy and has poor resolution.
9) The THEMIS camera was since March 2001, so images will be available in Sept-Oct. after their 6 month product generation and validation period.
Greg also explained that the THEMIS VIS is not capable of taking “true color” images because it does not have the proper filters for that. However, using the violet filter with the green and a red will produce an image that is close. Technically, all images from the VIS will be false color images. The data will be available on PDS, and anyone can combine the different bands to make their own “color” images. One of the problems with some of the wording in this area is that, what may be practical in application may not be technically correct. Although no “true color” images will be available from VIS, the combined images can be manipulated to approximate a true color photo. Some color information loss will occur but it will be minimal.
The VIS camera in THEMIS is a push-broom camera. It has five filters laminated to the surface of a 1024 x 1024 CCD element. These filters are aligned consecutively in the downtrack direction. Each filter is about 200 pixels long and 1024 pixels wide. The CCD is scanned about once every second, which is the time it takes for the Odyssey to move almost the width of a filter. Therefore, each filter is scanned just before it has crossed over into new territory. There is a 25 pixel row overlap, and this overlap is used to help align successive images together. The result is that the camera can obtain continuous images on each of the five filters at the same time. The only limitation to downtrack image length is the available memory.
The Visible Image Camera in THEMIS has filters in 5 visible bands, well, not quite.
The bands are:
1---- 0.870µm INFRARED
4---- 0.751µm RED - 780-622
3---- 0.652µm RED - 780-622
xxxxx---- no filter orange - 622-597
xxxxx---- no filter yellow - 597–577
5---- 0.553µm GREEN - 577-492
xxxxx---- no filter blue - 492-455
2---- 0.423µm VIOLET - 455-390
Notice that only four of the filters are in the visible range and one is in infrared. Also notice that there is no blue filter which is needed to make “true” color, RGB.
So what color is an image if it is not true color? It depends on your definition of true color. When most people say true color, they mean an image as it would appear to the human eye under normal lighting conditions. However, it could be said that an image taken through a 0.553µm Green filter and then reproduced with that same wavelength color is true color. It will be “green and white”, but it will be the same green that the filter allowed through when the image was taken. This can be very misleading, because when equivalent amounts of red and blue are added from corresponding exposures taken through the appropriate red and blue filters, the resulting photo may not contain any green at all. You can prove this to yourself by taking photos through various filters with your own camera.
All other pictures taken with the THEMIS camera are monochromic. Because they are exposed in infrared, all viewable images from infrared will be in false color.
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The massive, disk-shaped galaxy MACS 2129-1 spins twice as fast as the Milky Way does, but it's still not nearly as active. Hubble observations of the distant galaxy reveal that it hasn't made stars for some 10 billion years.
The third planet from the Sun is the only body in the universe on which humans have confirmed a presence of life.
Space matters to young people, a lot! My children, ages 3, 8, and 11, ask me every day if there's an ISS pass that night. They see the ISS and imagine the Astronauts looking back at them, and they are awestruck. I'm glad to have found these new forums.
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First dog in space died within hours. The dog Laika, the first living creature to orbit the Earth, did not live nearly as long as Soviet officials led the world to believe
Neutron stars are the densest And tiniest stars in the known universe and although they only have a radius of about 10 km (6 mi), they may have a mass of a few times that of the sun. They can rotate up to 60 times per second after they are born from a core-collapse supernova star explosion and have been known to spin as fast as 600 to 712 times per second because of their physics
NEPTUNE - Giant, spinning storms on Neptune are big enough to swallow the WHOLE EARTH! And when provoked, the itsy-bitsy invertebrates known as tardigrades can suspend their metabolism. In that state, they can survive temperatures of… 73 K (-328 degrees F) for days on end, making them hardy enough to endure being stranded on Neptune.
Interestingly, Uranus does not spin vertically like you would expect. Rather it rotates horizontally on its axis.
We need not have to worry much about the Great Attractor - The mysterious force that sucks-in several galaxies including our Milky Way because humanity is highly not likely to survive to experience that event!
The Andromeda Galaxy has at least two spiral arms, plus a ring of dust that may have come from the smaller galaxy M32. Astronomers think that it may have interacted more closely with Andromeda several hundred million years ago, when M32 plunged through the heart of its larger neighbor.
Galaxy W2246-0526 is by no means the largest or most massive galaxy we know of, but it radiates at 350 trillion times the luminosity of the Sun. If all galaxies were positioned an equal distance from us, WISE J224607.55-052634.9 (or W2246-0526 for short) would be the brightest.
Accelerating at 10 m/sec gets you going fast rapidly. I've heard we could overtake Voyager in about 3 weeks with constant acceleration. I like the Pilgrim Observer from the 70's approach to space travel with it's Saturn 5 launch to orbit and then NTR to travel to the planets with gravity on the ship with arms stowed and supported, speeding up then slowing down. Then while in orbit extending it's arms to rotate and have gravity along the living area's with 0g at the core I would include a lander to travel down to the surface of whatever planet it arrives at and perhaps a few more living arms for a larger crew (extending the ships length) Can't wait till we decide to get this going. also the Gateway foundation approach to a space station works for me as well, although I would put the escape pods to use sideways as sleeping quarters so the floor is correct and the use is not wasted currently they are to be pointed away from the center of axis and thus you'd have to climb down into them when needing to escape. if you're sleeping in them you would only need to detach and escape.
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