Space debris: Expert warns of increasing CubeSat collision risk

A Clyde-Space CubeSat in the Scottish test lab.

Credit: Clyde-Space

The increasing number of small 'CubeSat' satellites being launched combined with a relaxed attitude to debris mitigation could lead to hazards for all space users unless preventative measures are taken, warns a leading space debris expert from the University of Southampton.

Speaking today at the 65th International Astronautical Congress (IAC) 2014 in Toronto, Dr Hugh Lewis said that this combination leads to a growth in space debris, as a result of collisions between CubeSats and other objects in orbit.

CubeSats are small satellites (around 10x10x10cm) that are providing opportunities for companies to break into the space data and communications industries.

Despite many CubeSats not having any manoeuvring capability so they cannot avoid collisions during the mission or manoeuvre to a disposal orbit at their mission end, they are still perceived to have a low impact on the space debris environment.

However, despite guidelines requiring the satellites to deorbit within 25 years, some are being launched into high Earth orbits, which means their orbital lifetime could be much greater.

More than a third of all CubeSats launched to-date (around 160 between 2003 and 2013) are predicted to remain on-orbit for more than 25 years.

Since 2005, CubeSats have been involved in more than 360,000 close approaches of less than 5 km with other orbiting objects.

Dr Lewis says: "To reduce the risks, some effort is needed to engage with the growing small satellite community."

"All space users, not just those in the CubeSat community, who are taking the right steps should be encouraged to continue and, ultimately, lead on sustainable practices and debris mitigation activities.

"Those who are not yet engaged with this approach should be encouraged to do so. It's probably a matter of changing their perceptions of the risks and helping them to understand that there is a collective responsibility to ensure that outer space activities are sustainable so that future generations have the same opportunities to use space as we do."

Dr Lewis and his team used their Debris Analysis and Monitoring Architecture to the Geosynchronous Environment (DAMAGE) model to simulate three future CubeSat launch traffic scenarios until the year 2043.

By comparing these with close approach data from 2005 to 2013, the team found CubeSats are estimated to be involved in millions of close approaches over the next 30 years, with a handful leading to a collision.

Analysis of the close approaches found that most of the collision risk from CubeSats comes from high-speed encounters with large spacecraft.

In addition, many of these encounters were in Sun-synchronous orbits that are popular with remote sensing and Earth science satellites.

Dr Lewis adds: "By far the greatest risk comes from those with long lifetimes at altitudes of about 750 km. If CubeSats continue to be launched into long-lived orbits without any means of disposing of them, then they will contribute to the growing space debris hazard."

"This is not a responsible or sustainable practice, in my view. However, if efforts are made to limit the lifetimes, as some are already doing, then the risks will be reduced."

Increasing BPA levels in urine associated with worsening male sexual function

Increasing BPA levels in urine associated with worsening male sexual function

Increasing Bisphenol-A levels in urine are associated with worsening male sexual function, according to a Kaiser Permanente study appearing online in the Journal of Andrology.

Increasing urine BPA level is associated with decreased sexual desire, more difficulty having an erection, lower ejaculation strength and lower level of overall satisfaction with sex life, researchers said. The five-year study examined 427 workers in factories in China, comparing workers in BPA manufacturing facilities with a control group of workers in factories where no BPA was present.

BPA is an ingredient in manufacturing polycarbonate plastic and epoxy resins and is now contained in a wide variety of consumer products from baby bottles, plastic containers, and the resin lining of cans for food and beverages, to dental sealants. People can be exposed to BPA by using BPA-containing products.

In a previous related study, Kaiser Permanente researchers measured BPA exposure based on work history and environmental BPA exposure in the workplace (http://xnet.kp.org/newscenter/pressreleases/nat/2009/111109bpa.html). This new study measured urine BPA among participants and examined the correlation between their urine BPA level and their reported problems of sexual dysfunction.

"This is the first human study to show that high urine BPA is associated with lower male sexual function," said study lead author De-Kun Li, MD, PhD, a reproductive and perinatal epidemiologist at Kaiser Permanente's Division of Research in Oakland, Calif. "Also, even among men exposed to BPA from only environmental sources (no occupational exposure and with average BPA level lower than the average observed in the American population), there were indications of an increased risk of sexual dysfunction."

He explained that although the estimates in the environmentally exposed group were not statistically significant due to small sample size, this finding may enhance the understanding of the BPA effect in human populations with low-dose environmental exposure and have important public health implications.

The researchers observed a dose-response association between increasing urine BPA level and declining male sexual function. The observed negative association was consistent across all categories measuring male sexual dysfunction.

This study is the second part of Kaiser Permanente's ongoing research to look at BPA's reproductive effect in humans. Both studies are the first to look at BPA's reproductive effect in humans. The adverse effect of BPA on the male reproductive system previously had been examined in animal studies only.