Freak Space Weather Responsible for Satellite Failures

 

Prominence Eruption from the sun, with a coronal mass ejection
Image showing a prominence eruption, with a resultant coronal mass ejection (CME), as captured by NASA’s Solar Dynamics Observatory.

A recent study has suggested that freak space weather may be responsible for disrupting satellite communications. A group of researchers, working at the Massachusetts Institute of Technology, have discovered that the output of electromagnetic radiation from the sun is responsible for dysfunction of the satellite technology that orbits the Earth. Understanding these failures could pinpoint areas of future improvement in satellite design.

Space weather causes satellite failures

These geostationary satellites remain fixed at a specific location above the Earth, for the duration of their function. As the Earth rotates, the satellite makes an orbit that allows it to remain “in step,” thereby keeping it at the same position, all year round. Many of these devices are responsible for relaying satellite television signals and Internet communications, representing a fundamental technology that many people simply take for granted.

However, these satellites are constructed to last a finite length of time, around 15 years. During its humble service, the technology is persistently bombarded with high energy particles from solar flares and geomagnetic storms. Initially, this does not present a significant problem, since the fragile elements of these satellites are concealed by protective shielding. Unfortunately, after the devices are exposed to electromagnetic radiation over a protracted period, the internal electronics begin to degrade. This, in turn, causes the satellite to perform poorly and eventually malfunction.

Solar cycle shown in stages
Solar cycle 23, showing 11 years in the life of the sun. The cycle starts at solar minimum, reaches solar maximum in 2001, and then returns back to solar minimum (2006).

According to Whitney Lohmeyer, who works in MIT’s Department of Aeronautics and Astronautics, understanding how space weather impacts geostationary satellites could provide telling clues on how to design satellites to improve their tolerance to the harsh environmental conditions of space:

“If we can understand how the environment affects these satellites, and we can design to improve the satellites to be more tolerant, then it would be very beneficial not just in cost, but also in efficiency.”

Lohmeyer expresses the importance of satellite communications in everyday life, stating that public demand has increased considerably. People are using these satellites more than ever, craving fast, high-bandwidth communication. As a consequence, Lohmeyer calls for a changeup in the design of next-generation satellites to endure recent space weather conditions, which had not previously encountered.

The European Space Agency (ESA) has also raised concern over the impact of the solar cycle upon satellite communications. Last year, the ESA outlined plans to establish a chain of monitoring stations to investigate the influence of solar max on satellite communications systems. It’s thought, during the solar max, large solar flares could contribute towards the output of damaging electromagnetic radiation.

The Study

The group published their findings in Space Weather, using data from a telecommunications organization in the United Kingdom, called Inmarsat, and sought to investigate the space weather observed at the time of a number of satellite failures.

A total of eight satellites were monitored over a period of 16 years, with over 26 hard failures reported. This constituted a whopping 665,000 hours of operation, for which telemetry data was obtained for the individual satellites studied.

One of the critical internal components, the amplifier, was found to be damaged during failure events. Between 1996 and 2012, the majority of glitches corresponded with “… high-energy electron activity” during the tail-end of the solar cycle, resulting in anomalies in 13 solid-state power amplifiers (SSPAs).

Armed with this knowledge, the researchers speculated that particle flux accrued inside the satellites over time, generating a harmful charge that disrupted the amplifiers. The amplifier is critical to the satellites proper function, serving to strengthen the signal, before beaming it back to Earth.

Is the Kp index an unreliable measure of geomagnetic activity?

Upon encountering a hard failure, the researchers matched up the weather conditions, which had been recorded by a number of space weather satellites. By measuring the geomagnetic activity, using the Kp index, researchers found some startling results. The satellites’ internal amplifiers would often experience malfunctions during times of low Kp index results (three or less). This is a highly significant finding, as current radiation models deem such Kp measurements to be safe.

The latest satellites are already being designed to take into consideration the influence of hazardous space weather. Radiation models are used to anticipate the intensity of the radiation a particular satellite is likely to encounter throughout its many years of operation. Assistant Professor Kerry Cahoy, who worked with Lohmeyer on the study, indicated that such exposure varies from satellite to satellite, based upon its orbit. Cahoy also outlines the limitations of current radiation models, which fail to take into consideration the highly diverse space weather conditions that satellites are subjected to.

Outdated radiation models

The authors allude to several problems, associated with overseeing satellite function. Firstly, when an orbiting satellite experiences any malfunction, researchers are not simply able to retrieve the device and perform their analyses.

Envisat satellite in construction
ESA’s Envisat satellite under construction in S5 building.

Lohmeyer also points to a “disconnect” between the technicians that work on satellites and the organizations responsible for forecasting space weather conditions. Ordinarily, the space weather community provides a forecasting facility and alerts the technicians on potential space weather hazards. Unfortunately, according to Lohmeyer, the implications of these warnings are often poorly understood.

In light of the revelations of their study, Cahoy and Lohmeyer tentatively speculate that the Kp index may not be the most effective indication of radiation exposure.

Although the latest satellites have auxiliary amplifiers, which operate in the event of a failure, these too eventually suffer from the effects of penetrating electromagnetic radiation. According to Lohmeyer, when companies are investing $200 million in designing and assembling a satellite, accurately “… quantifying and understanding the space environment…” is of critical to enhancing its design.

The researchers call for further investigation into freak space weather and hope their studies will be instrumental in the future of satellite design.

By: James Fenner

Space Weather Journal

Journal Press Release Source

MIT AeroAstro Website

Red Orbit Link

3 Responses to "Freak Space Weather Responsible for Satellite Failures"

  1. Rocks   September 16, 2013 at 9:53 pm

    Hey fella,s…what u need is rocks hanging out there to measure all them “rad,s”…..those metal sat,s are gett,n fried by all that CME every time it pops a quasar (the torch) at them !!!!

    Reply

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