While space debris was the uncontrolled adversary in the award-winning space thriller film "Gravity," space debris, also known as "space junk," is an ongoing real-life concern for teams managing satellites orbiting Earth, including NOAA-NASA's Suomi National Polar-orbiting Partnership, or Suomi NPP, satellite. It is not unusual for satellites that have the capability of maneuvering to be repositioned to avoid debris or to maintain the proper orbit.
On an otherwise quiet Sunday on September 28, the Suomi NPP mission team was monitoring a possible close approach of a debris object. By early evening, the risk was assessed to be high enough to start planning a spacecraft maneuver to put the satellite into a safer zone, out of the path of the object classified in a size range of 4 inches up to 3.3 feet.
The animation depicts the distribution and movement of man-made objects orbiting Earth.
Image Credit: NASA Orbital Debris Program Office at JSC
It was determined that the object (travelling at almost 17,000 mph) was approaching at a nearly "head on" angle, and could potentially only miss the Suomi NPP satellite by approximately 300 feet on Tuesday, September 30, if no action was taken. With that knowledge, the decision was made at 1:30 p.m. on Monday, September 29, for NOAA's Satellite Operations Facility, or NSOF, in Suitland, Maryland, to reposition Suomi NPP. Operational control as well as planning and execution of all Suomi NPP maneuvers take place at NSOF.
"Because Suomi NPP moves at a similar speed as the debris object, if there had been an impact, it would have occurred at a combined speed of nearly 35,000 mph. This would have been catastrophic not only to the satellite, but would result in thousands of pieces of new debris," said Harry Solomon, Mission Manager for Suomi NPP at NASA's Goddard Space Flight Center.
Space around Earth is littered with numerous man-made objects that could potentially collide with operating spacecraft and each other (creating more debris). There are more than 20,000 objects being monitored by the U.S. Department of Defense for satellite managers around the world.
Only about 1,000 of those 20,000 objects are operating spacecraft. The rest of the monitored space debris ranges in size from the size of a softball, to massive rocket bodies, all orbiting uncontrolled at relative speeds averaging about 22,300 mph in low-Earth orbit, where the majority of the objects reside.
Yet it is the unknown, often smaller, untracked objects that pose the biggest threat. "If a spacecraft is lost due to being hit by debris, the odds are the satellite will be hit by something the trackers can't see," said Nicholas Johnson, NASA chief scientist (retired) for orbital debris at Johnson Space Center in Houston.
That is exactly the scenario Solomon and his counterpart, Martin England, mission operations engineering lead at NSOF hope will never happen.
Risk Team Monitors Unmanned Missions Threats for NOAA and NASA
While NASA's Johnson Space Center manages monitored debris threats for spacecraft related to U.S. manned missions such as the International Space Station, the responsibility for unmanned missions managed by NASA falls to the Conjunction Assessment Risk Analysis, or CARA, team operating out of NASA Goddard.
About seven days before a potential threat, information from the Department of Defense is analyzed by the CARA team to evaluate predicted close approaches. CARA monitors and provides updated information about potential threats to satellite mission managers who then make a decision about the need to reposition their satellites in a procedure known as a Risk Mitigation Maneuver.
Since Suomi NPP's launch in October 2011, this recent reposition was the fourth Risk Mitigation Maneuver to avoid space debris. In this case, the object was a section of a Thorad-Agena launch vehicle used between 1966 and1972 primarily for Corona U.S. reconnaisssance satellites.
A previous Suomi NPP risk mitigation maneuver in January 2014 avoided a discarded booster from a Delta 1 launch vehicle, a type of rocket made in the United States for a variety of space missions from 1960 to 1990. There is also a significant amount of debris in Suomi NPP's orbit from the Chinese Fengyun-1C, a meteorological satellite China destroyed in January 2007 in a test of an anti-satellite missile. Another threat near Suomi NPP's orbit is the debris resulting from a 2009 collision of a functioning commercial communications satellite and a defunct Russian satellite.
Suomi NPP's job is to collect environmental observations of atmosphere, ocean and land for both NOAA's weather and oceanography operational missions and NASA's research mission to continue the long-term climate record to better understand the Earth's climate and long-term trends.
To accomplish those goals, the satellite maintains a position on orbit such that the desired path across the ground does not vary by more than 20 km (12 miles) on each side. This orbit is adjusted with regular planned maneuvers to maintain the proper orbit and angles for best information collection. But if a Risk Mitigation Maneuver to avoid space debris were to necessitate moving out of that desired collection zone, then yet another maneuver would be necessary to return to the optimum orbit position. These unplanned maneuvers tap into the finite amount of fuel on satellites and could potentially shorten mission life of a spacecraft if fuel is used more quickly than anticipated.
The amount of space debris is not constant. It generally increases every year, sometimes generated from debris collisions, which can potentially create additional debris fragments. But there are also debris reductions. One tracked object generally falls back to Earth daily, sometimes burning up to nothing upon re-entry, or falling into water or the large areas of low population density.
In addition, there are also natural events that help control debris. The sun is currently going through a period known as solar maximum, the term for a high period of solar activity. The increased number of sunspots and solar storms during solar maximum takes place approximately every 11 years. During this period, the extent of Earth's atmosphere increases due to solar heat generated by the increased amount of solar activity. As the atmosphere extends to higher altitudes, debris at these altitudes are then subjected to increased friction, known as drag, and as a result, space debris typically fall to Earth at a higher rate during solar maximum.
The Suomi NPP mission is a bridge between NOAA and NASA legacy Earth observing missions and NOAA's next-generation Joint Polar Satellite System, or JPSS. The next satellite, JPSS-1, is targeted for launch in early 2017.
Audrey Haar | Eurek Alert!
DGIST develops 20 times faster biosensor
24.04.2017 | DGIST (Daegu Gyeongbuk Institute of Science and Technology)
New quantum liquid crystals may play role in future of computers
21.04.2017 | California Institute of Technology
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
24.04.2017 | Physics and Astronomy
24.04.2017 | Materials Sciences
24.04.2017 | Life Sciences