Taurus Constellation

Sensor to monitor orbital debris outside space station

The International Space Station isn’t the only spacecraft orbiting the Earth. In fact, it is accompanied by the Hubble Space Telescope, satellites within the Earth Observing System, and more than 1,000 other operational spacecraft and CubeSats. In addition to spacecraft, bits of orbital debris - human-made objects no longer serving a purpose in space - are also in orbit.

With an estimated more than 100 million pieces of orbital debris measuring smaller than one centimeter currently in Earth’s orbit, they can be too small to track, but many are large enough to cause damage to operational spacecraft.

The space station has orbital debris shields in place to protect from debris less than 1.5 centimeters in size. Larger debris pieces are tracked by ground control, and if needed, the space station thrusters can be used to safely move station away from the debris.

The Space Debris Sensor (SDS) will monitor the small debris environment around the space station for two to three years, recording instances of debris between the sizes of .05mm to.5mm. Objects larger than 3 mm are monitored from the ground. It will launch to station in the trunk of a SpaceX Dragon during a resupply mission no earlier than Dec. 12.

Orbital debris as small as .3mm may pose a danger to human spaceflight and robotic missions.

“Debris this small has the potential to damage exposed thermal protection systems, spacesuits, windows and unshielded sensitive equipment,” said Joseph Hamilton, the project’s principal investigator. “On the space station, it can create sharp edges on handholds along the path of spacewalkers, which can also cause damage to the suits.”

Once it is mounted on the exterior of the Columbus module aboard the space station, the sensor will provide near-real-time impact detection and recording capabilities.

Using a three-layered acoustic system, the SDS characterizes the size, speed, direction and density of these small particles. The first two layers are meant to be penetrated by the debris. This dual-film system provides the time, location and speed of the debris, while the final layer - a Lexan backstop - provides the density of the object.

The first and second layers of the SDS are identical, equipped with acoustic sensors and .075mm wide resistive lines. If a piece of debris damages the first layer, it cuts through one or more of the resistive lines before impacting and going through the second layer. Finally, the debris hits the backstop plate.

Although the backstop won’t be used to return any of the collected samples, combined with the first two layers, it gives researchers valuable data about the debris that impacts the SDS while in orbit.

“The backstop has sensors to measure how hard it is hit to estimate the kinetic energy of the impacting object,” said Hamilton. “By combining this with velocity and size measurements from the first two layers, we hope to calculate the density of the object.”

The acoustic sensors within the first two layers measure the impact time and location using a simple triangulation algorithm. Finally, combining impact timing and location data provides impact and direction measurements of the debris.

Data gathered during the SDS investigation will help researchers map the entire orbital debris population and plan future sensors beyond the space station and low-Earth orbit, where the risk of damage from orbital debris is even higher to spacecraft.

“The orbital debris environment is constantly changing and needs to be continually monitored,” said Hamilton. “While the upper atmosphere causes debris in low orbits to decay, new launches and new events in space will add to the population.”

The Galaxy is a beautiful and mysterious place full of wonder

Cut Timber

The window for saving the world’s coral reefs is rapidly closing

The world’s reefs are under siege from global warming, according to a novel study published today in the prestigious journal Science

The world’s reefs are under siege from global warming, according to a novel study published today in the prestigious journal Science.

For the first time, an international team of researchers has measured the escalating rate of coral bleaching at locations throughout the tropics over the past four decades. The study documents a dramatic shortening of the gap between pairs of bleaching events, threatening the future existence of these iconic ecosystems and the livelihoods of many millions of people.

“The time between bleaching events at each location has diminished five-fold in the past 3-4 decades, from once every 25-30 years in the early 1980s to an average of just once every six years since 2010,” says lead author Prof Terry Hughes, Director of the ARC Centre of Excellence for Coral Reef Studies (Coral CoE).

“Before the 1980s, mass bleaching of corals was unheard of, even during strong El Niño conditions, but now repeated bouts of regional-scale bleaching and mass mortality of corals has become the new normal around the world as temperatures continue to rise.”

The study establishes a transition from a period before the 1980s when bleaching only occurred locally, to an intermediate stage in the 1980s and 1990s when mass bleaching was first recorded during warmer than average El Niño conditions, and finally to the current era when climate-driven bleaching is now occurring throughout ENSO cycles.

The researchers show that tropical sea temperatures are warmer today during cooler than average La Niña conditions than they were 40 years ago during El Niño periods.

“Coral bleaching is a stress response caused by exposure of coral reefs to elevated ocean temperatures. When bleaching is severe and prolonged, many of the corals die. It takes at least a decade to replace even the fastest-growing species,” explained co-author Prof Andrew Baird of Coral CoE.

“Reefs have entered a distinctive human-dominated era - the Anthropocene,” said co-author, Dr C. Mark Eakin of the National Oceanic & Atmospheric Administration, USA. “The climate has warmed rapidly in the past 50 years, first making El Niños dangerous for corals, and now we’re seeing the emergence of bleaching in every hot summer.” For example, the Great Barrier Reef has now bleached four times since 1998, including for the first time during back-to-back events in 2016 and 2017, causing unprecedented damage. Yet the Australia government continues to support fossil fuels.

“We hope our stark results will help spur on the stronger action needed to reduce greenhouse gases in Australia, the United States and elsewhere,” says Prof Hughes.

IMAGE….A researcher from the ARC Centre of Excellence for Coral Reef Studies surveys the bleached/dead corals at Zenith Reef, Nov 2016. Credit Andreas Dietzel

Mova Globes