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The ozone layer is a region in the Earth’s atmosphere that contains high concentrations of ozone. Ozone is three molecules of oxygen bonded together, and so it has the chemical symbol O3. The ozone layer contains more than 91% of the ozone in the Earth’s atmosphere. Because it absorbs ultraviolet radiation from the Sun, the ozone layer is vital to the evolution and survival of life on Earth.
Ozone in the Earth’s atmosphere is created when sunlight strikes oxygen molecules which consist of two oxygen atoms bonded together (O2). This splits it into two separate oxygen atoms which float in the atmosphere until they bond with other oxygen molecules creating ozone (O3). Ozone is unstable, though, and further ultraviolet radiation continues to break up the ozone into oxygen molecules and single oxygen atoms. This combination and breakdown is going all the time in the ozone layer.
The ozone layer is special to life because it absorbs ultraviolet radiation from the Sun in a very specific wavelength – UV-B radiation, between 315-280 nanometers in wavelength. It’s this UV-B radiation which gives us sunburns and can even cause cancer with long term radiation. Without the ozone layer, we would receive much more harmful radiation from the Sun.
Of course, one of the big worries in the last few years is the problem of ozone depletion. Certain manmade chemicals, like nitric oxide and chlorofluorocarbons break down ozone molecules, stopping them from being able to absorb ultraviolet radiation. A single molecule of one of these free radicals can break down more than 100,000 ozone molecules.
Satellites observing the Earth’s atmosphere discovered that the ongoing use of these chemicals were causing the ozone layer to thin out. Ozone layers declined at a rate of 4% per decade, mostly over the Earth’s northern and southern poles. Many countries enacted bans of ozone-destroying chemicals in 1978, and in the last few years scientists have determined that the rate of ozone depletion is slowing down.
Jupiter's rings. Image Credit: University of Maryland
We’re familiar with the rings of Saturn, but did you know that Jupiter has rings too? The rings of Jupiter were first discovered by the Voyager 1 spacecraft when it passed by Jupiter in 1979. The rings were investigated in more detail by NASA’s Galileo spacecraft during the 1990s. It was during the 1990s that Galileo and ground-based observations made a complete count of the number of Jupiter’s rings. So, how many rings does Jupiter have?
Jupiter is known to have 4 sets of rings: the halo ring, the main ring, the Amalthea gossamer ring, and the Thebe gossamer ring.
The halo ring is closest into Jupiter starting at a radius of 92,000 km and extending out to a radius of 122,500 km. The halo ring has a total width of 12,500 km.
Next is the main ring. It starts at 122,500 km and extends out to 129,000 km. It has a total width of only 6,500 km.
Outside these two major rings are the gossamer rings. These are very faint rings that are shepherded by two of Jupiter’s moons. The first is the Amalthea gossamer ring, which is shepherded by Jupiter’s moon Amalthea. It starts at a radius of 129,000 km from Jupiter and goes out to the orbit of Amalthea at 182,000 km.
Overlapping the Amalthea ring is the Thebe gossamer ring. It starts at a radius of 129,000 and goes out to a radius of 226,000 km.
How many rings does Jupiter have? The answer is four. Of course, it’s always possible that new rings will be discovered around Jupiter as new and better spacecraft and telescopes examine the planet.
Artist impression of the Milky Way. Image credit: NASA
Here are some beautiful pics of the Milky Way Galaxy. It’s important to remember that we live inside the Milky Way Galaxy, so there’s no way to show a true photograph of what the Milky Way looks like. We can see pictures of the Milky Way from inside it, or see artist illustrations of what the Milky Way might look like from outside.
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This Milky Way Galaxy picture shows what our galaxy would look like from above. You can see its spiral arms, dense core and the thin halo. The Milky Way is a common barred spiral galaxy. There are billions more just like it in the Universe.
Milky Way in infrared. Image credit: COBE
This picture of the Milky Way was captured by NASA’s COBE satellite. This photograph was taken using the infrared spectrum, which allows astronomers to peer through the gas and dust that normally obscures the center of the Milky Way.
The plane of the Milky Way, recorded with the Chandra satellite in three colours: Photons with energies between 0.5 and 1keV appear red, those between 1 and 3keV green, and those between 3 and 7keV blue. Discrete sources are indicated by circles. Image: Mikhail Revnivtsev
This image of the Milky Way Galaxy was taken with the Chandra X-Ray Observatory, which can see in the X-Ray spectrum. In this view, only high energy emissions are visible, such as the radiation emitted from black holes and other high energy objects.
Artist's concept shows young, blue stars encircling a supermassive black hole at the core of a spiral galaxy like the Milky Way.Credit: NASA, ESA, and A. Schaller (for STScI)
Here’s an artist’s impression of what a galaxy like the Milky Way might have looked like early in its history. This image shows a supermassive black hole with young blue stars circling it.
Milky_Way_infrared_mosaic. Credit: Spitzer Space Telescope
This is a mosaic image of the Milky Way captured by NASA’s Spitzer Space Telescope. It was built up by several photographs taken by Spitzer, which sees in the infrared spectrum, and can peer through obscuring dust.
Throughout history, the definition of what a planet is has changed and meant various things at the same time depending on who was defining it. Objects like the Sun, which we would now scoff at defining as a planet, was once considered just that, and so was the Moon. Ceres, discovered in 1801, was originally thought to be a planet until astronomer discovered Pallas that has a similar orbit. Astronomers, even using the technology of their time, were able to tell that these objects were not planets. The famous astronomer Sir William Herschel suggested the name “asteroids” which stuck. Asteroids were then accepted as a distinct category.
Several years ago, you may have said that a planet is one of the nine large celestial bodies that orbits the Sun. However, new technology, which made the discovery of many new celestial bodies in various regions, such as the Kuiper Belt, possible also made determining what a planet is more difficult. While a number of people suggested various definitions over the years, none of them were widely accepted.
The issue came to a head in 2005 when an object larger than Pluto is was discovered beyond the Kuiper Belt. This object, which is now called Eris, was a source of division among many. Some astronomers wanted Eris to be the tenth planet while others considered it to be just another asteroid, despite the fact that it is larger than Pluto is. The International Astronomical Union (IAU), which usually resolves disputes like this, met in 2005 at a conference, but despite debating the issue, they did not come up with an agreed upon definition. The matter was resumed in summer of 2006 at the next IAU conference.
In August 2006, the IAU finally agreed upon a definition for a planet. The IAU’s official definition was, “A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.” An object that has cleared the neighborhood of its orbit is of sufficient size for its gravity to force other objects of similar size out of its orbit. In addition to defining what a planet is, the IAU also created a new category of dwarf planets, which Pluto was reclassified as, and Eris and several other objects were also put in that category. The definition has had severe opposition, especially with many people angry at the demotion of Pluto.
Discovery Education has eight projects on the Solar System that you can do with a class or a single child. Many of them are also great projects for a science fair or a report. This website also has games to play and some ideas on how to get your students or children interested in space as well as a quiz to make sure that the material has been mastered.
Cool Science Projects has some suggestions on various projects for a science fair as well as some background material on the Solar System.
Enchanted Learning has a number of Solar System crafts that are simple enough for young children probably in kindergarten or grades 1 through 3. There are also coloring pages about the Solar System that can be printed.
The AOK Corral has a project painting a glow in the dark Solar System, which is a great twist on an old classic. You can take the idea of using the glow in the dark paint a step further and create a glow in the dark mural for a kid’s room.
How Stuff Works has some great projects for kids including one on how to make your own planetarium and learning how to create your own astrolabe.
A to Z Home’s Cool Homeschooling has a ton of links to great projects and experiments you can try. Some of these links let you figure out your weight on other planets. You can also get information on all the planets in the Solar System.
One of the best resources for your space needs is NASA. NASA has materials for children including games to play and projects for science fairs as well as information on the planets and all the other objects in the Solar System. They also have materials for children of different ages and even resources for college students. NASA even has information on how to get a guest speaker from NASA at your school.
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Those fearful folks who have worried about the Large Hadron Collider creating a black hole that could swallow the Earth have probably been feeling pretty safe while the giant particle accelerator is still offline. But hopefully they haven’t read the latest Physical Review Letters . It includes a paper that explains how researchers at Dartmouth have figured out a way to create a tiny quantum-sized black hole in their lab, with no LHC required.
In their paper, the researchers show that a magnetic field-pulsed microwave transmission line containing an array of superconducting quantum interference devices, or SQUIDs, not only reproduces physics similar to that of a radiating black hole, but does so in a system where the high energy and quantum mechanical properties are well understood and can be directly controlled in the laboratory. The paper states, “Thus, in principle, this setup enables the exploration of analogue quantum gravitational effects.”
“We can also manipulate the strength of the applied magnetic field so that the SQUID array can be used to probe black hole radiation beyond what was considered by Hawking,” said Miles Blencowe, an author on the paper and a professor of physics and astronomy at Dartmouth.
Creating a black hole would allow researchers to better understand what physicist Stephen Hawking proposed more than 35 years ago: black holes are not totally void of activity; they emit photons, which is now known as Hawking radiation.
“Hawking famously showed that black holes radiate energy according to a thermal spectrum,” said co-author Paul Nation. “His calculations relied on assumptions about the physics of ultra-high energies and quantum gravity. Because we can’t yet take measurements from real black holes, we need a way to recreate this phenomenon in the lab in order to study it, to validate it.”
This is not the first proposed imitation black hole, Nation said. Other proposed schemes to create a black hole include using supersonic fluid flows, ultracold bose-einstein condensates and nonlinear fiber optic cables. However, these ideas wouldn’t work as well to study Hawking radiation because the radiation in these methods is incredibly weak or otherwise masked by commonplace radiation due to unavoidable heating of the device, making it very difficult to detect. “In addition to being able to study analogue quantum gravity effects, the new, SQUID-based proposal may be a more straightforward method to detect the Hawking radiation,” said Blencowe.
Did you get a chance to watch the IYA “Live” Telescope today? We were on! And now we’ve got some exciting news for you… You can watch via your iPhone on TVU! That’s right… We’re now broadcasting on Channel 79924 as Northern and Southern Galactic TV. You can watch Galactic TV via your iPhone by installing TVUPlayer from the App Store! Now… Are you ready for today’s video? Then hang on tight as we take you a walk to NGC 247, the Burbidge Galaxy Chain and the Running Man Nebula! It’s time to rock….
Skies were clear and dark in Central Victoria and it was time to fire up the IYA Live Telescope and get the party started. We’re testing out a new system that will allow more viewers an opportunity to see through the virtual eyepiece and we’re ready to get the scope set on a something really far out. Our first object? NGC 247 and the Burbidge Galaxy Chain in the constellation of Cetus…
This interesting chain of four MCG galaxies lies only 18 arc minutes NNE of NGC 247, a giant member of the nearby Sculptor Group. (NGC 247 itself is 9th-magnitude but of very low surface brightness, which can make it tough to spot in a smaller scope.) In itself, NGC 247 is an Intermediate spiral galaxy located over 12 million light years away. Talk about a long distance phone call!
The northernmost and southernmost members of the chain are relatively easy to pick up in a 17.5″ scope. That’s aperture – not tube length! Bwahahahahaaaaa….
Last object for the night? Lace up your Nikes, cuz’ we’re heading for NGC 1977, the “Running Man Nebula” in Orion…
NGC 1973/5/7 is a reflection nebula 1/2 degree northeast of the Orion Nebula. The three NGC objects are divided by darker regions.
It was discovered on January 18, 1784 by Sir William Herschel, seasoned sky veterans know this area by its nickname ‘‘the Running Man’’. Consisting of three separate areas of emission and reflection nebulae that seem to be visually connected, 1,500-light-year-distant NGC 1977/1975/1973 complex would be spectacular on its own if weren’t so close to M42! The conjoining nebula is whispery soft, its dark lanes created by interstellar dust and fine needle-like shards of carbon. Illuminating the gases is its fueling source, the multiple star 42 Orionis—a prized double on many lists. Through a telescope, this lovely triangle of bright nebulae and its several enshrouded stars make a wonderful region for exploration. Can you see the Running Man within?
As of the time of this posting, the scope was still up and running… along with the nebula! We’re making every effort when the sky is clear to keep the view coming at you, dear reader. So keep checking back often and enjoy the new iPhone application! If things keep working the way they should, you should be able to enjoy a video loop of many of our best objects at all times… We hope!
So you think you know your universe? We’ve got our own top 10 list on the most interesting facts about the Universe.
1. It was hot when it was young
The most widely accepted cosmological model is that of the Big Bang. This was proven since the discovery of the cosmic microwave background radiation or CMBR. Although, strictly speaking, no one knows exactly what ‘banged’, we know from extrapolation that the Universe was infinitely hot at birth, cooling down as it expanded.
In fact, even only within minutes of expansion, scientists predict its temperature to have been about a billion Kelvin. Moving backward to 1 second, it is said to have been at 10 billion Kelvin. For comparison, today’s universe is found to have an average temperature of only 2.725 Kelvin.
2. It will be cold when it grows old
Observations made especially on galaxies farthest from us show that the Universe is expanding at an accelerated rate. This, and data that show that the Universe is cooling allows us to believe that the most probable ending for our universe is that of a Big Freeze.
That is, it will be devoid of any usable heat (energy). It is due to this prediction that the Big Freeze is also known as the Heat Death.Accurate measurements made by the Wilkinson Microwave Anisotropy Probe (WMAP) on the current geometry and density of the Universe favor such an ending.
3. The Universe spans a diameter of over 150 billion light years
Current estimates as with regards to the size of the Universe pegs it at a width of 150 billion light years. Although it may seem peculiarly inconsistent with the age of the Universe, which you’ll read about next, this value is easily understood once you consider the fact that the Universe is expanding at an accelerated rate.
4. The Universe is 13.7 billion years old
If you think that is amazing, perhaps equally remarkable is the fact that we know this to better than 1% precision. Credit goes to the WMAP team for gathering all the information needed to come up with this number. The information is based on measurements made on the CMBR.
Older methods which have contributed to confirming this value include measurements of the abundances of certain radioactive nuclei. Observations made on globular clusters, which contain the oldest stars, have also pointed to values close to this.
5. The Earth is not flat – but the Universe is
Based on Einstein’s Theory of General Relativity, there are three possible shapes that the Universe may take: open, closed, and flat. Once again, measurements by WMAP on the CMBR have revealed a monumental confirmation – the Universe is flat.
Combining this geometry and the idea of an invisible entity known as dark energy coincides with the widely accepted ultimate fate of our universe, which as stated earlier, is a Big Freeze.
6. Large Scale Structures of the Universe
Considering only the largest structures, the Universe is made up of filaments, voids, superclusters, and galaxy groups and clusters. By combining galaxy groups and clusters, we come up with superclusters. Some superclusters in turn form part of walls, which are also parts of filaments.
The vast empty spaces are known as voids. That the Universe is clumped together in certain parts and empty in others is consistent with measurements of the CMBR that show slight variations in temperature during its earliest stages of development.
7. A huge chunk of it is made up of things we can’t see
Different wavelengths in the electromagnetic spectrum such as those of radio waves, infrared, x-rays, and visible light have allowed us to peer into the cosmos and ‘see’ huge portions of it. Unfortunately, an even larger portion cannot be seen by any of these frequencies.
And yet, certain phenomena such as gravitational lensing, temperature distributions, orbital velocities and rotational speeds of galaxies, and all others that are evidence of a missing mass justify their probable existence. Specifically, these observations show that dark matter exists. Another invisible entity known as dark energy, is believed to be the reason why galaxies are speeding away at an accelerated rate.
8. There is no such thing as the Universe’s center
Nope. The earth is not the center of the Universe. It’s not even the center of the galaxy. And no again, our galaxy is not the entire universe, neither is it the center. Don’t hold your breath but the Universe has no center. Every galaxy is expanding away from one another.
9. Its members are in a hurry to be as far away from each other as possible
The members that we are talking about are the galaxies. As mentioned earlier, they are rushing away from each other at increasing rates. In fact, prior to the findings of most recently gathered data, it was believed that the Universe might end in a Big Rip. That is, everything, down to the atoms, would be ripped apart.
This idea stemmed from this observed accelerated rate of expansion. Scientists who supported this radically catastrophic ending believed that this kind of expansion would go on forever, and thus would force everything to be ripped apart.
10. To gain a deeper understanding of it, we need to study structures smaller than the atom
Ever since cosmologists started to trace events backward in time based on the Big Bang model, their views, which focused only on the very large, got smaller and smaller. They knew, that by extrapolating backward, they would be led into a universe that was very hot, very dense, very tiny, and governed by extremely high energies.
These conditions were definitely within the realm of particle physics, or the study of the very small. Hence, the most recent studies of both cosmology and particle physics saw an inevitable marriage between the two.
There you have it. Feel free to come up with a longer list of your own.
Greetings, fellow SkyWatchers! Are you ready for the weekend? Then let’s enjoy the nights ahead as we fly along the Milky Way on the wings of the Swan and hunt down some very different star clusters in the night with the Fox. Do you need a smile? Then you’ll find one with with a delightful asterism called the “Coat Hanger”! How about a Herschel challenge? We’ve got that, too. In the mood to just stargaze? Then stick around – because the Perseid Meteor Shower hasn’t ended just yet. (We’ve got something very special inside here to show you!) Time to get out your telescopes and binoculars and I’ll see you outside…
Friday, August 21, 2009 – On this date in 1993, the Mars Observer was lost. . . But you can’t miss Mars at its peak just before dawn!
Tonight it’s time for us to fly with the ‘‘Swan’’ as the graceful arch of the Milky Way turns overhead. We’ll start by taking a look at a bright star cluster that’s equally great in either binoculars or telescope, M39.
Located about a fist-width northeast of Deneb (Alpha Cygni), you will easily see a couple of dozen stars in a triangular pattern. M39 (RA 21 31 48 Dec +48 27 00) is particularly beautiful because it will seem almost three-dimensional against its backdrop of fainter stars. Younger than the Coma Berenices cluster, and older than the Pleiades, the estimated age of M39 is at least 230 million years. This loose, bright, galactic cluster is around 800 light-years away. Its members are all main sequence stars, and the brightest of them are beginning to evolve into giants.
For more of a challenge, try dropping about a degree south-southwest (RA 21 29 00 Dec +47 08 00) for NGC 7082, also known as H VII.52. Although it is a less rich, less bright, and far less studied open cluster, at magnitude 7.5 NGC 7082 is within range of binoculars and is on many open cluster observing lists. With only a handful of bright stars to NGC 7082’s credit, larger telescopes are needed to resolve out many of the fainter members. Be sure to mark your notes for both objects!
Saturday, August 22, 2009 – Born this date in 1833 was Samuel Pierpont Langley, who investigated the relationship between solar phenomena and meteorology. Is that why we always have clouds when solar activity is at its best?
Tonight we’ll hunt with the ‘‘Fox’’ as we head to Vulpecula to try two more open star cluster studies. The first can be done easily with large binoculars or a low power scope. It’s a rich beauty in the constellation of Vulpecula but is more easily found by moving around 3 degrees southeast of Beta Cygni (RA 19 35 48 Dec +25 13 00).
Known as Stock 1, this stellar swarm contains 50 or so members of varying magnitudes, which you will return to often. With a visual magnitude of near 5, loose associations of stars—like Stock clusters—are the subject of recent research. The latest information indicates that the members of this cluster are truly associated with one another.
A little more than a degree to the northeast is NGC 6815 (RA 19 40 44 Dec +26 45 32). Although NGC 6815 is a slightly more compressed open cluster, it has no real status among deep-sky objects, but it is another one to add to your collection of things to do and see!
Sunday, August 23, 2009 – On this date in 1609, Galileo demonstrated the telescope for the first time. Tonight we’ll aim our own optics at an asterism known as the ‘‘Coat Hanger,’’ which is also known as Brocchi’s Cluster, or Collinder 399. Let the colorful double star Beta Cygni—Albireo—be your guide as you move about 4 degrees to its south-southwest (RA 19 25 24 Dec +20 11 00). You will know this cluster when you see it, because it really does look like a coat hanger!
Enjoy its red stars! Discovered by Al Sufi in 964 AD, this 3.5 magnitude collection of stars was again recorded by Hodierna. Thanks to its extended size of more than 60′ it escaped the catalogs of both Messier and Herschel. Only around a half dozen stars share the same proper motion, which may make it a cluster much like the Pleiades, but studies suggest it is merely an asterism—but one with two binary stars at its heart.
And for larger scopes? Fade east to the last prominent star in the cluster (RA 19 30 36 Dec +20 16 00) and power up. NGC 6802 awaits you! At near magnitude 9, Herschel VI.14 is a well-compressed open cluster of faint members. The subject of ongoing research in stellar evolution, this 100,000-year old cluster is on many observing challenge lists!
Over the weekend, be sure to keep an eye out for stray Perseid meteors, because the show hasn’t ended yet! Although activity has slowed considerably, your chances are above average of catching a bright streak while you’re out enjoying the stars. It was a wonderful year for the Perseids and even if you were clouded out, we’ve still managed to catch the action for you…
Many thanks to John Chumack of Chumack Observatory (Dayton, Ohio) for all of his hard work in capturing and editing the footage from his All Sky Camera from the nights of August 11-14th. He’s trimmed the video to 5 frames per second and within this less than one minute clip, you’ll see over 200 meteors and the Moon rise three times! Were the Perseids a success? You bet. Just as John how he finished his film… “I ended it with the brightest…” said John, “A -8 magnitude fireball!”
Keep looking up! You’ll never know when it might be your lucky night…
This week’s awesome images are (in order of appearance): M39, NGC 7082, Stock 1, NGC 6815 (credit—Palomar Observatory, courtesy of Caltech), Collinder 399 (credit—Gil Estel), NGC 6802 (credit—Palomar Observatory, courtesy of Caltech) and Perseid Meteor Storm Video courtesy of John Chumack. We thank you so much!!
Navigating a spacecraft through the heavens has been compared to sailing a ship on the open seas or driving a vehicle on a long, cross country journey. Analogies are necessary, since spacecraft navigation is performed by a relatively small sampling of the human race, and the job usually involves doing things that have never been done before. Those of us who have trouble making sense of a road map here on Earth stand in awe of what these celestial navigators can accomplish.
Literally, this is rocket science.
In simplest terms, spacecraft navigation entails determining where the spacecraft is and keeping it on course to the desired destination. But it’s not as easy as just getting from Point A (Earth) to Point B (a planet or other body in our solar system.) These are not fixed positions in space. Navigators must meet the challenges of calculating the exact speeds and orientations of a rotating Earth, a rotating target destination, as well as a moving spacecraft, while all are simultaneously traveling in their own orbits around the Sun. Chris Potts points to Gusev Crater on Mars on January 4, 2004, after the MER navigation team landed the Spirit rover on Mars with unprecedented accuracy. Photo courtesy of Chris Potts
Chris Potts, who helped lead the navigation teams for the Mars Exploration Rovers (MER), compared the target requirements of landing the Spirit rover inside a specific crater on Mars to being able to shoot a basketball through a hoop 9000 miles away. “Not only do you have to make the shot perfectly without the ball touching the rim, but the timing has to be perfect, so you make the shot exactly as the buzzer sounds,” he said.
Ken Williams was the Navigation Team Chief for the Stardust mission’s return of pristine samples of a comet back to Earth. For a successful re-entry and landing at a precise location in Utah, the navigation team had to target the return capsule’s entry to a specific point in the Earth’s atmosphere to within eight 100ths of a degree, a feat that’s been compared to hitting the eye of a sewing needle with a piece of thread from across a room.
Navigation is essential to every robotic mission, and while mission success hinges on how well the navigation team performs, navigators aren’t usually found in the limelight, sitting up on stage for a press conference. Typically that’s reserved for the mission scientists and designers. The navigators, seemingly, work behind the scenes, manning the trenches in relative anonymity.
But I had the opportunity to talk to a few spacecraft navigators, learning more about their job and discovering the innate qualities of those who guide our spacecraft to places beyond. Neil Mottinger. Image courtesy Neil Mottinger.
Neil Mottinger has been part of numerous missions since he started working at the Jet Propulsion Laboratory in 1967. He assisted with some of the early lunar and planetary missions, and developed some of the software that navigators still use today.
There are several different sub-disciplines to spacecraft navigation, and one of Mottinger’s specialties is orbit determination. “Orbit determination is knowing where the spacecraft is and where it’s going,” said Mottinger, who currently works with the Mars Reconnaissance Orbiter (MRO) mission and the upcoming LCROSS (Lunar Crater Observation and Sensing Satellite) mission to the moon. “It starts with predicting the trajectory where the spacecraft will be immediately after launch so that the Deep Space Network (DSN) knows where to point their antenna and on what frequency to expect the signal.” The DSN consists of a network of extremely sensitive deep space communications antennas at three locations: Goldstone, California; Madrid, Spain; and Canberra, Australia. The strategic placement approximately 120 degrees apart on Earth’s surface allows constant observation of spacecraft as the Earth rotates.
Since there’s no GPS in outer space, navigators process the radiometric tracking data received from the DSN to determine the spacecraft’s position and velocity. They also use optical data, where the spacecraft takes a picture of the star background to help refine the spacecraft’s trajectory.
For many years, Mottinger worked with a group that provided navigation support for the launch of over 100 spacecraft. “I never got attached to any one mission since right after a launch we moved on the next mission,” Mottinger said. But now he stays with missions longer and has been with the MRO mission for the better part of three years. Mottinger is thrilled with the scientific data this mission has returned. “We have to provide accurate predictions of where the spacecraft is going to be. Then the engineers know how to orient spacecraft so that the scientists can make their observations,” he said. “If we do our job, the scientists can see a landslide on Mars or look at specific areas on the planet. If our predictions are wrong, the cameras are pointed in the wrong direction. Navigation is integral to the whole process of ensuring mission success.” An active volcano on Io, taken by the New Horizons spacecraft. Credit: NASA
Mottinger said that typically one doesn’t think of navigators as scientists, only as a means to an end for the scientists to get results. However, sometimes scientific by-products come from navigation. The most famous instance involved the Voyager mission when navigator Linda Morabito discovered a volcano on Jupiter’s moon Io from looking at optical navigation images. In the Lunar Orbiter missions, navigators realized there were large concentrations of mass, (now called mascons) underneath the moon’s surface that were accelerating spacecraft in orbit.
Additionally, the science used in navigation has improved dramatically over the years. “When you look at the types of things we didn’t understand when I first started versus what we know now, it’s overwhelming,” said Mottinger. For example navigators can now create very accurate models of solar pressure – how particles of sunlight push against a spacecraft and alter its trajectory — which includes not only how sunlight is reflected from different surfaces of the spacecraft, but also the re-radiation of energy absorbed by the solar panels and radiated out the back side.
Additionally ephemerides, the tables navigators use to obtain the positions of astronomical objects, have also improved in accuracy over the years. “The devil is in the details,” said Mottinger. “Navigation is getting to be an incredibly precise game.”
Like many who work at JPL, Mottinger enjoys talking to schools or community groups to share the excitement and recent discoveries of space exploration. “It’s important to be out there telling our message to get people excited about what we’re doing,” he said. “And the public is entitled to be excited, because they’re paying the bill.”
Several years ago Mottinger returned to his hometown of Oswego, Illinois to talk to students about his job as a navigator. Sitting in the classroom was a young Chris Potts, who decided spacecraft navigation was the career he wanted to pursue. Potts, who has been at JPL since 1984, was the Deputy Navigation Team Chief for MER and now works with the Dawn Mission that is en route to orbit two asteroids, Ceres and Vesta. Chris Potts and Neil Mottinger with a model of the Mars Exploration Rover at JPL. Photo courtesy of Chris Potts
Potts’ specialty is flight path control. This involves firing the propulsion system to alter the spacecraft’s velocity or trajectory, known as Trajectory Correction Maneuvers (TCM). “That includes understanding the spacecraft’s control capabilities and determining any limitations,” said Potts. “You determine when you’re going to fire the propulsion system, how often and the objective of each maneuver. You also have to evaluate the delivery requirements, to make sure you can land within a crater on Mars, for example, and minimize risk along the way.”
The design aspect is Potts’ favorite part of the job. “You try to develop a strategy that puts all the pieces together,” he said. “You have to talk with the mission scientists and understand what their requirements are, and then know what the spacecraft can do. It’s like people who have an old car and they’ve been around it so long, they know how to get the most out of that vehicle. Taking advantage of what the spacecraft does well and working around its limitations feeds into the design of a strategy that pulls it all together to make it work.”
Much of Potts’ work involves simulations and testing. “We see how the spacecraft behaves, and try out different strategies to improve it for our situation,” he said. “The navigation section has a whole ‘toolbox’ of software that we’re able to use.” Artist concept of the Dawn spacecraft. Credit: NASA
The Dawn spacecraft uses an ion engine, and this is the first time Potts has worked with a low thrust propulsion system. “It’s quite a different mission,” he said. “The concerns are little bit different than other missions because the thrust is so efficient. One of the things you worry about is not having enough time to make any corrections that are needed. Although the thrust is low, over time it builds up quite a velocity change and you’re always designing trajectories and changing commands to make sure the ion engine is firing in the right direction. If there’s any kind of spacecraft fault or hiccup along the way, you have to scramble, and some future events might have to be moved around.” Dawn will arrive at Vesta in 2011.
Potts enjoys being part of the excitement of all the different missions at JPL. “I really enjoy working with some extremely intelligent and talented people here and you can definitely sense the passion for the work that they do,” he said. “Sometimes that can be intimidating, but you realize that everyone has their own talent to offer, and everyone helps drive you to do your best here. We get to do a variety of interesting work, and it’s very challenging. No two days are the same.”
One of the rewards of his job, Potts said, is seeing the fruition of his work come to light in scientific discoveries. “With the Stardust sample return, to watch the capsule land right where it was supposed to in Utah was very rewarding,” he said. “And to see the scientists get their hands on that data and start to perform their investigations, you sense how thrilled and excited they are to finally get to work on their lifelong ambition.”
Potts and Mottinger both worked on the Stardust mission under the leadership of Ken Williams. Williams worked at JPL for several years, but currently is employed by KinetX, a private engineering firm specializing in aerospace technology and software development. At present, KinetX provides navigation support for the New Horizons mission to Pluto, as well as the MESSENGER (Mercury Surface Space Environment Geochemistry and Ranging) mission to Mercury, and Williams is MESSENGER’s navigation team chief. Unlike Mottinger and Potts, Williams hasn’t always been involved in space missions and his career in navigation evolved from a background in physics. He worked at the Applied Physics Lab at Johns Hopkins University before coming to work at JPL in 1994. Ken Williams of KinetX.
Williams’ favorite part of being a navigator is finding and solving interesting technical problems. “That’s what gets my interest,” he said. “MESSENGER certainly has a number of those. We flew by Earth once, Venus twice and Mercury twice. We’ll have to fly by Mercury one more time before we finally go into orbit on the fourth encounter. Finding a trajectory that does all those things successfully is a very interesting technical problem that I’m very glad to be involved with. We have to consider all sorts of constraints, too, such as keeping the spacecraft pointed away from the sun so that the components don’t get too warm.”
As a Navigation Team Chief, Williams coordinates all the sub-disciplines of orbit determination, flight path control, and optical navigation along with the needs of mission scientists in terms of observations when they encounter a planet or comet.
Williams, too, enjoys the exhilaration of being in the thick of the action in important space missions. “I suppose it’s like being in a battle, or in a basketball or football game,” he said. “You feel the excitement of seeing events unfold, and responding to any anomalies or surprises that come up. And when it’s all done you have a tremendous sense of satisfaction.”
His experiences with Stardust’s return to Earth stand out as a highlight. “Getting all that effort coordinated and getting the spacecraft down successfully was probably the single most rewarding experience in all the time I was at JPL,” he said. “On nearly every mission I’ve worked on there has been a time where you have a sense of euphoria about having the spacecraft be in the right place at the right time. That’s a good feeling to have.” The Stardust Mission Navigation Team was presented with Popular Mechanics’ Breakthrough Award. Said Team Chief Ken Williams: “The day we took this picture, I felt a strong sense of camaraderie with all these folks after everything had worked so well. They’re a very talented group of people who did a tremendous job.” FRONT ROW – left to right:Tung-Han You, Ken Williams, Prem Menon. 2nd Row: Roby Wilson, Katherine Nakazono, Julie Kangas. 3RD Row: Daniel Lyons, Ram Ramachand, Bhat Shyam Bhaskaran, Cliff Helfrich, Jeff Tooley, David Jefferson, Dimitri Gerasimatos, Paul Thompson, Neil Mottinger. Last row: Darren Baird, Jae Lee, Chris Potts, Tim McElrath, Brian Kennedy
Although leaving JPL was a difficult decision, Williams enjoys his experiences at a private company. “It would have been easy to stay at JPL and be what they call a ‘greybeard’ in terms of having experience, but after Stardust, I liked the challenge of leading a navigation team and growing in technical areas,” he said. “I thought there would be a better opportunity to do that with a small team in a small company, and I thought KinetX was a good place to accomplish that.“
Quite the opposite of a ‘greybeard’ is navigator Emily Gist. She has been at JPL for 4 years and is part of the navigation team for the Cassini mission at Saturn. Like Potts, she works in flight path control, helping to plan the trajectory and estimate the future position of the spacecraft, and to control the corrections required to achieve the mission objectives. Artist concept of the Cassini spacecraft at Saturn. Credit: NASA
She takes great satisfaction knowing she is helping to facilitate exploration. “The Saturnian system is more beautiful than most would have imagined and more diverse than previously known,” she said. “The information Cassini has provided has enlightened us all. More specifically I love how much I learn each and every day at JPL and working on the Cassini Mission.”
As part of the ‘next generation’ of navigators, Gist enjoys the challenging environment that JPL provides. “We had an Operations Readiness Test on Cassini where the team was tested to see how we would react to a failure or fault on the spacecraft in an operational environment,” she said. “The senior engineers weren’t in play so the newer generation had to figure it out on our own and we did an excellent job. It made me proud of all the folks I work with. They are truly talented people.”
Gist said gender has never been an issue in her job as a navigator. “JPL has a wonderfully diverse staff and while there are not very many female navigators we are not treated differently,” she said. “I am pretty biased, but I think what we lack in quantity we make up for in quality. I work with some amazing women.”
“Additionally, I feel fortunate to live in a time and society where regardless of gender one can find the thing they want to do and do it to the best of their ability. I love being an engineer and what I try to convey to young women is that they can love anything they want, even if it’s math and science, without fear that it’s a less feminine job.”
The hardest question for all the navigators to answer was if they had a least favorite part of the job. They cited the usual problems with any job: not enough time and too much paperwork. And stress comes with the job. “Deadlines, especially working at JPL, are very real,” said Potts. “If you’re not prepared for a critical event in the mission, you usually don’t get a second chance. There’s a lot riding on getting your job done properly.”
But all the navigators emphasized the importance of the team aspect in their job. “You look for the inherent quality of the team,” said Mottinger. “I had a project manager who said that a team catches each other’s mistakes and the whole is greater than the sum of the parts. Everything is done in a spirit of camaraderie, and there’s no such thing as a stupid question.” Galileo at Jupiter. Credit: NASA
But seeking individual limelight just doesn’t seem to be in a navigator’s makeup.
“I’m more comfortable working behind the scenes than doing an interview,” said Potts. “When I know I’ve done my job, and contributed to the mission success, that’s enough for me.”
“I am fine with my work being behind the scenes,” added Gist. “However when I consider the work the engineers before me and around me have done I sometimes feel they should get more recognition.”
Williams feels, in general, the field of navigation itself should get more recognition. “I think scientists and people who do purely hardware systems underestimate the difficulty of what navigators have to do,” he said. “It would be nice if we got more recognition from our peers just from the standpoint of being able to influence how missions are planned and designed to begin with so that navigation issues can be addressed before launch and not only left for us to deal with after launch. I feel more strongly about that than any recognition of my own accomplishments.”
Williams said that what navigators do is more of an art form. “It’s not reducible to a set of algorithms that can be stored on board a flight system like power or propulsion, for example. It’s constant refining.”
And are navigators bothered by the sometimes long and odd hours their job requires? “No,” said Mottinger, “I wouldn’t trade it for anything. There’s nothing else like it.”
