Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - DeCAS (The first real-time monitoring device able to determine the impact area of space vehicles’ fragments during re-entry into the Earth’s atmosphere and minimize risks for people and property)

Teaser

In the last decade the space debris issue has been in the spotlight, with more than 13,000 artificial objects currently orbiting around the Earth, including around 1,700 operating satellites, most of which are destined to re-enter the atmosphere and hopefully burn out. NASA...

Summary

In the last decade the space debris issue has been in the spotlight, with more than 13,000 artificial objects currently orbiting around the Earth, including around 1,700 operating satellites, most of which are destined to re-enter the atmosphere and hopefully burn out. NASA estimates that one piece returns to the Earth each day, while around 40 large space debris objects (>800 kg) re-enter the atmosphere each year. Unfortunately, 10-40% of satellite mass survives re-entry and impacts the Earth’s surface, posing serious hazards to people, property, and air traffic.

The atmosphere is dense enough to dissolve most objects owing to air resistance and heat, but 10-40% of mass survives and impacts the Earth’s surface, posing serious hazard to both people and their property.

For instance, out of the 2008 spacecraft ATV-1 mass of 12.3 tons, 3.5 tons in 183 fragments survived re-entry, 28.4% of the mass. Several events like the 2003 Shuttle Columbia disintegration and spreading over a large inhabited area in Texas induced national and international space agencies to adopt Space Debris Mitigation (SDM) policies for minimizing the risk for population. However, the effectiveness of the current SDM plans is hindered by the following limiting factors:
• The impossibility to precisely predict the impact area of surviving fragments. Space debris spread over long, thin ground footprints (e.g. for ATV-1 ~817km by 30km), depending on several factors, such as the flight features of each fragment, local wind, atmospheric condition. Currently, only rough estimations of the fragment impact area can be made. Even few minutes before the impact, these factors determine a positional error in the Earth-impact point of up to 5,000 km.
• The high cost of safety measures in case of dangerous satellite re-entries. Very wide areas potentially concerned have to be closed (with strong direct and indirect economic costs), also due to the inaccurate calculation of the footprint probability area. In 2012 EUROCONTROL (European intergovernmental organization for air traffic management) was notified by Russian authorities to close the whole Europe airspace for 2 hours for the re-entry of the Russian Phobos-Grunt (calculated cost ~€20 Million).

• The increasing risk caused by the large number of satellite re-entries on the earth. Even a falling fragment of 300 grams can be catastrophic for an aircraft (US Federal Aviation Administration data), and over the last decades, more than 1,400 tons of materials have survived re-entry. With the increased number and turnover of satellites, this is pushing higher the risk for casualties, and the worldwide collision risk with space debris for flights has been estimated in 3x10-4 (the generally acceptable risk in aviation is 1x10-7).

While space agencies (NASA, ESA) are adopting increasingly stricter policies for mitigating risks associated to space debris collisions, satellite operators are in search for reliable solutions able to enhance safety measures in the re-entry phase, ensure compliance with regulations, and minimize the impact on spacecraft design performances and costs.

Aviosonic has developed and patented DeCAS, the first high-precision monitoring system for tracking space debris during the re-entry phase, able to precisely determine both the break-up impact point (at an altitude of around 78-84 km) and the area interested by the subsequent fragmentation, and promptly notify safety agencies about potential danger for people and property.

In the framework of the Phase 1 project, both technological and business feasibility study was run.

As a conclusion, the outcomes of the project clearly showed the technological feasibility and that conditions exist for the implementation of the DeCAS technology.

Work performed

During Phase 1 project activities for designing the hardware system by ensuring its compliance with end users’ needs, and business analyses aimed at assessing the market requirements for the adoption and expected profitability of the system was achieved pursuing the following objectives:

• Technological developments: Starting from the available system design, selection and integration of the various hardware components (antennas, sensors, modems, gyroscopes, accelerometers, GPS receivers, power system) in a functional prototype was done.

In this way, the bill of materials fulfilling the customers’ requirements in terms of overall size, weight, power absorption, power supply, interface features, and also the overall cost was defined.

Particular care was devoted to the system’s outer case, which has to ensure high resistance and radio frequency transparency. Specific tests on the components will be conducted so to validate the required software functionalities (activation through re-entry message, data processing, broadcast of alert message), as already successfully tested in space by using the satellite software infrastructure during the D-SAT mission.

• Business Developments:

(A) Consolidation of the business model by interacting with key stakeholders (satellite manufacturers/operators, insurance companies, and public safety agencies).

(B) Cost-benefit analysis in order to gauge the willingness to pay of each potential customer segment and define the most suitable pricing strategy.

(C) Economic/financial projections, with accurate estimation of the overall investment to be borne for the system development and validation, as well as for the production and operating costs to market the solution.

Final results

Currently, the monitoring of the re-entry phase of space vehicles is performed only for space shuttles and large satellites which are considered potentially dangerous in case they fall on sensitive areas. There are basically three different observing techniques for keeping track of space objects in the proximity of Earth atmosphere:
1. Radar systems, either through ground station or satellite networks. Radars can detect and track debris objects larger than 10 cm up to an altitude of ~2,000 km. The main drawback is that to ensure a wide space coverage, the network needs to rely on several ground stations disseminated on the Earth surface, which makes them very expensive to build and maintain. In order to identify and discriminate satellites and space debris, they need to operate at very high frequencies, with related high energy consumption and electromagnetic noise.
2. Optical observations. Optical telescopes catch the sunlight reflected from debris larger than ~1 m, and are usually used for monitoring higher Earth orbits, up to ~40,000 km. The use of digital image processing enables automated observations and near-real time analysis. Even in this case, there are structural issues linked to high costs for the facilities, as well as inaccuracy in both the detection and tracking of objects.
3. Laser observation. Short laser pulses are transmitted towards a satellite or space object, and then are reflected back from reflector prisms installed on-board. The return pulses are detected by telescopes, obtaining the distance of the object very precisely. This method is hindered by the difficulty to track decaying objects, whose orbits change very rapidly, thus making it difficult to point the laser beam accurately.
The above systems are very expensive to build, run and maintain and present 3 key technical drawbacks:
• Even when they accurately track the re-entering object, orbit predictions are highly inaccurate, with a positional error in the re-entry point of up to 5,000 km even few minutes before the break up in the atmosphere.
• None of them is able to effectively cover 100% of the Earth surface.
• None is able to determine in real-time the impact area of fragments surviving breakup in the atmosphere. Currently, only few software tools (e.g. NASA’s DAS and ORSAT) perform analysis for determining space vehicles impact risk, based on trajectory and atmospheric models. These tools are highly theoretical, with very limited calibration data, and are used solely for risk evaluation purposes before the launch (e.g. providing info on the mass and objects expected to survive, expected impact velocity, etc.).
DeCAS is the only system able to track in real time and with maximum accuracy the position and fragment footprint of a re-entering vehicle, since the prediction is based on actual data collected during and after the breakup by the DeCAS smart fragment. It does not require the enormous expenses of ground station networks to be operated, because it is embedded in each space vehicles and transmits real data on its actual position.
DeCAS enables to easily monitor all the upper stage components and satellites, thus enhancing world governments’ capacity to monitor and mitigate potential risks, which currently is focused only on shuttles and few big satellites/space vehicles. It will minimize risk for people and properties, and support space operators in reducing the casualty risk of their missions, comply with international regulations, and lower insurance premiums.

Website & more info

More info: http://www.aviosonic.it.