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A)Microsatellites: Making light work of orbit and attitude control
Microsatellites have to be very light — every gram counts. The same applies to the gyroscopes used to sense the satellite’s orientation when in orbit. A novel prototype is seven times lighter and significantly smaller than earlier systems.
When you observe the sky on a clear night, the twinkling objects you see may not only be stars but also human-made satellites. Occasionally visible from Earth, these orbiting spacecraft come in different sizes, from large telecommunications and TV satellites to the smaller scientific satellites that serve as space laboratories. The measuring instruments they carry on board send back data to researchers on the ground for use in various projects. An example is the TET satellite, which scientists are using to test the capacity of new measuring systems to withstand the inhospitable conditions of space missions. If they pass these tests, they can be incorporated in other small satellites.
One such system is the gyroscope developed by researchers at the Fraunhofer Institute for Reliability and Microintegration IZM in Berlin in collaboration with the engineering specialists at Astro- und Feinwerktechnik Adlershof GmbH. Satellites use gyroscopic sensors to determine their orientation relative to their orbital position as a backup system if their star tracker is inoperative or if star visibility is degraded. Such attitude control systems require at least three gyroscopes, one for each direction of movement. They measure the satellite’s rate of rotation and calculate its orientation on the basis of the most recent reliable data supplied by the star tracker.
The gyroscopes must be able to withstand the extreme temperature fluctuations encountered in low Earth orbit — where temperatures range between minus 40 and plus 80 degrees Celsius — without damage, and remain operable for several years despite the high solar radiation. A further requirement is that they should be as small and light as possible, because payload capacity is limited and every gram saved on the launch pad immediately translates into lower costs. Finally, the gyroscopes must be energy-efficient, because microsatellites only have a tiny solar panel to generate the power they need.
No larger than a wallet
“Our gyroscope withstands the inhospitable conditions of space, and is also significantly smaller, lighter, and consumes less energy than comparable solutions,” says Michael Scheiding, managing director of Astro- und Feinwerktechnik Adlershof GmbH. Instead of the usual 7.5 kilograms, it weighs in at a little less than one kilo. And the scientists have also significantly reduced its volume. While similar devices are usually about the size of a shoe box, the new gyroscope measures just 10 by 14 by 3 centimeters, i.e. no larger than a wallet. The researchers’ ultimate aim is to halve the size of the system yet again. Another advantage is that it requires approximately half as much energy as comparable devices.
How did the researchers achieve this result? To find out, it is necessary to take a look inside the fiber-optic gyroscope. Its main component is a fiber coil, a core with one to two kilometers of fiber wrapped around it. The longer the fiber, the more accurate the gyroscope. “We have reduced the length of the fiber to 400 meters, but can still obtain the same level of accuracy,” says Marcus Heimann, a researcher at IZM. “One of the things we did to achieve this was to select more efficient optical components.” The splice points between the different fibers that link the light source, the detector, and the coil have also been optimized. The scientists will be presenting their prototype at the Sensor + Test trade show in Nürnberg from June 3 to 5 (Hall 12, Booth 12-537). Visitors can test how accurately the gyroscope determines the rate of rotation by making it rotate on a turntable.
The new gyroscope could one day help a satellite bus like this with attitude detection: the platform of the approximately one-meter long TET-1 satellite.
Credit: © Astro Feinwerktechnik Adlershof GmbH
B)India puts satellite into orbit around Mars
India triumphed in its first interplanetary mission, placing a satellite into orbit around Mars on Wednesday and catapulting the country into an elite club of deep-space explorers.
In scenes broadcast live on Indian TV, scientists broke into wild cheers as the orbiter’s engines completed 24 minutes of burn time to manoeuvre the spacecraft into its designated place around the red planet.
“We have gone beyond the boundaries of human enterprise and innovation,” Prime Minister Narendra Modi said in a live broadcast from the Indian Space and Research Organization’s command centre in the southern tech hub of Bangalore.
“We have navigated our craft through a route known to very few,” Modi said, congratulating the scientists and “all my fellow Indians on this historic occasion.”
Scientists described the final stages of the Mars Orbiter Mission, affectionately nicknamed MOM, as flawless. The success marks a milestone for the space program in demonstrating that it can conduct complex missions and act as a global launch pad for commercial, navigational and research satellites.
Indian Space Research Organization (ISRO) scientists and engineers watch Prime Minister Narendra Modi, left, on screens after India’s Mars orbiter successfully entered at their Spacecraft Control Center in the southern Indian city of Bangalore. (Abhishek N. Chinnappa/Reuters)
Reaching the fourth planet from the sun is a major feat for the developing country of 1.2 billion people, most of whom are poor. At the same time, India has a robust scientific and technical educational system that has produced millions of software programmers, engineers and doctors.
India describes MOM as the first successful Mars mission on a maiden attempt by any country, although the European Space Agency, a consortium of several nations, also did it on its first Mars mission in 2003.
Rival China is also expanding its space exploration program with a space station in orbit and the landing of a lunar rover on the moon earlier this year, although it has not sent a satellite to Mars.
Astronomy students who gathered at the Nehru Planetarium in New Delhi for Mars-themed learning activities and games were elated by the mission’s success.
“I am proud to be born in a country that can do anything and succeed,” said Kashish, 12, who uses only one name.
Another 12-year-old, Mansha Khanna, said she was so inspired she wanted to become “a scientist or an astronaut, and do research about other planets.”
Mars orbit attempts have been mostly unsuccessful
Getting a spaceship successfully into orbit around Mars is no easy task. More than half the world’s previous attempts — 23 out of 41 missions — have failed. India wanted this spacecraft, also called Mangalyaan, meaning “Mars craft” in Hindi, to be a global advertisement for its ability in designing, planning and managing a difficult, deep-space mission.
India has already conducted dozens of successful satellite launches, including sending up the Chandrayaan-1 lunar orbiter, which discovered key evidence of water on the moon in 2008. And it plans new scientific missions, including putting a rover on the moon.
But India “is likely to be somewhat limited because we can’t afford to spend that much money in pure science exploration and in an exercise of the imagination,” said D. Raghunandan of the Delhi Science Forum, a group that promotes the study of science.
The space agency’s focus will remain on developing technologies for commercial and navigational satellite applications — services that could bring in significant revenues from companies or governments seeking to place their own satellites or research equipment in space.
“If we’re going to earn money, we’re going to do it on that,” Raghunandan said.
U.S. space agency NASA, which has conducted 15 successful missions to Mars, including a spacecraft that arrived in orbit on Sunday, congratulated India in a Twitter message welcoming MOM to studying the red planet.
India’s 1,350-kilogram orbiter will now circle the planet for at least six months, with solar-powered instruments gathering scientific data that may shed light on Martian weather systems as well as what happened to the water that is believed to have existed once on Mars.
Data can be compared to concurrent NASA mission
It also will search Mars for methane, a key chemical in life processes on Earth that could also come from geological processes. None of the instruments will send back enough data to answer these questions definitively, but experts say the data will help them better understand how planets form and what conditions might make life possible.
“It’s yet another source of information. Mars is gradually unveiling its secrets to science and humanity, and the Indian mission is yet another means of unveiling this enigma that Mars presents,” said space expert Roger Franzen, the technical program manager at the Australian National University’s Research School of Astronomy and Astrophysics.
Scientists said it was helpful that MOM’s data will reflect the same time period as data being collected by NASA’s newest Maven mission, allowing the two data sets to be compared for better understanding.
The U.S. has two more satellites circling the planet at the moment, as well as two rovers rolling across the rocky Martian surface.
India was particularly proud that MOM was developed with homegrown technology and for a bargain price of about $75 million US — a cost that Modi quipped was lower than many Hollywood movie budgets. NASA’s much larger Maven mission cost nearly 10 times as much, at $671 million.
“Today not only has a dream come true, but we have created history for India, for ISRO, and for the world,” said Vipparthi Adimurthy of the Indian Institute of Space Science and Technology.
C)65th International Astronautical Congress | Cubesat Revolution, Spotty Compliance with Debris Rules Fuel Dangerous Congestion in Low Earth Orbit
TORONTO — The world’s rocket and satellite owners are doing a mediocre job in respecting debris-mitigation rules, especially in low Earth orbit, where debris proliferation is the ugly underside of the fast-growing small-satellite and microsatellite market, government and industry officials said.
Twelve years after a grouping of the world’s space powers published what it thought were modest guidelines asking that satellite and rocket owners take steps to remove their hardware from low Earth orbit within 25 years after its mission, a sizable portion of them are paying little attention to the rule.
The French space agency, CNES, studied 12 years of debris-mitigation practices, 2000-2012, and found that 40 percent of satellites and rocket bodies are left in low Earth orbit at altitudes high enough to make it impossible for them to re-enter within the 25-year window specified in the rules.
“There is no clear trend toward improvement over the years,” said Juan Carlos Dolado Perez of CNES, who presented the results of the study at the 65th International Astronautical Congress here. “There is still a real effort to be done.”
Raising or lowering a satellite or rocket stage’s orbit to remove it from the busiest orbital highways takes fuel, which a satellite owner would prefer to use to extend mission life. Launch services providers would like to use that energy to carry more satellite payload.
Bad enough when satellite operations deal mainly with multimillion-dollar spacecraft, the situation threatens to get worse as Moore’s Law — which predicts that the number of transistors on a computer microprocessor will double every two years or so — enables ever-smaller nests of technologies to be placed on small-satellite platforms for a price that universities and startup companies can afford.
The owners of some of these satellites have not registered with the International Telecommunication Union even though the spacecraft are broadcasting signals, creating potential interference issues. Many are launched in groups, on shoestring budgets, with no onboard propulsion to assure they can be sufficiently lowered at the end of their operating lives to meet the 25-year rule.
“Most [debris] mitigation guidelines were not meant for these very small satellites,” said Heiner Klinkrad, director of the European Space Agency’s Space Debris Office in Darmstadt, Germany. “Cubesats are slipping through the net. They are all going to the same altitudes, which means they will constitute a kind of curtain, which increases collision risks.”
Objects deployed from the international space station, or near the station’s 400-kilometer altitude, will naturally be drawn into Earth’s atmosphere and destroyed well within 25 years. It is at higher altitudes, above 500 kilometers, where lies the problem.
“Many of the cubesats are going to altitudes higher than 500 kilometers,” said Marcello Valdatta of the University of Bologna, Italy. He said the rules regarding cubesats — a generic term for satellites usually weighing less than 2 kilograms — are vague.
The only solution may be to design an inexpensive, lightweight “plug and fly” kit that would deploy at the end of the cubesat’s life, creating drag and forcing its atmospheric re-entry within 25 years.
Several researchers, presenting the results of their analysis of what has been happening with the microsatellites launched in recent years — the relatively high failure rates in orbit, the mounting debris — adopted an almost apologetic tone, saying they did not want to smother a young and dynamic industry with regulations.
“It’s not about bashing the cubesat community at all,” said Hugh G. Lewis of Britain’s University of Southampton, who studied the orbits and disposition of cubesats in recent years as part of a project funded by the European Commission’s Framework Seven Program for Research.
Lewis’ data came from ESA’s catalog of orbital objects and from work done by T.S. Kelso, senior research astrodynamicist at Analytical Graphics’ Center for Space Standards and Innovation in Colorado Springs, Colorado.
The data point to more than 350,000 “conjunctions,” or close encounters in which a cubesat and another space object came to within 5 kilometers of each other, between 2005 and June of this year. As the number of cubesats in orbit has increased, so has the number of conjunctions involving them.
Only 1 percent of conjunctions in 2007 involved a cubesat, Lewis said. For the first nine months of 2014, cubesats accounted for 5 percent of the total.
Depending on a satellite’s size and shape, it is all but certain to remain in orbit more than 25 years after retirement if its altitude is above 650 kilometers.
Some 160 cubesats were launched between 2003 and 2013. Their launch rate has increased sharply since then. One-third of them operate in orbits that are too high to meet the 25-year rule, and in many cases they could not meet a 50-year rule, Lewis said.
Phil Smith, senior analyst at the Tauri Group space consultancy of Alexandria, Virginia, in a presentation on the dynamism of the cubesat sector — a 300 percent increase in launches between 2012 and 2013, and a 63 percent increase, to 150 satellites, expected in 2014 — agreed that many of these satellites are heading into orbits that are inconsistent with the 25-year rule.
Several speakers said cubesat owners will need to come up with a debris-mitigation solution on their own, or face the risk that an in-orbit collision in a popular orbit for weather or science or military satellites leads to government regulations that could cripple the industry.
The proliferation of cubesats and nanosats was also a subject of discussion at the Advanced Maui Optical and Space Surveillance Technologies conference in Maui, Hawaii, in September, where experts considered the question of whether a licensing regime is needed.
“We have to operate safely, but not stifle the innovation,” said Josef Koller, space policy adviser for the deputy assistant secretary of defense for space policy.
U.S. Strategic Command, which provides space situational awareness information for the Defense Department, has said it can track items as small as about 10 centimeters, the standard length of the side of a cubesat. While a new ground-based S-band radar known as the Space Fence is expected to enable Strategic Command to track even smaller objects, it is not yet clear how many cubesats would be added to the catalog.
One issue is that because cubesats are often launched in tandem into close-proximity orbits, it can be difficult to distinguish one from another.
The Secure World Foundation, a nonprofit organization dedicated to space sustainability, plans to develop a handbook for new operators in the next year — rules of the road that, if adopted by organizations from universities to governments, would help reduce the threat.
The book is necessary because some cubesat owners “may not have a lot of experience in doing this in a responsible manner,” said Brian Weeden, technical adviser at the Secure World Foundation.
By Peter B. de Selding
SpaceNews staff writer Mike Gruss contributed to this article from Maui, Hawaii.
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