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Nasa estimates the odds of someone being struck by a falling part of the spacecraft at one in 3,200

Helium balloons are known for pulling things up, but they could be a great way to drag defunct satellites down to Earth, a team of engineers says.

Researchers in EPFL's Computer Vision Laboratory developed a computer-based modeling service that generates a 3D image from up to thousands of 2D shots, with all the processing done in the cloud. Since April, the EPFL startup Pix4D has been offering the modeling service with a fourth dimension: time. Now, individuals and small businesses looking for fast, cheap, large-scale 3D models can get them without investing in heavy processing, the company states. With Pix4D, users upload a series of photos of an object, and within 30 minutes they have a 3D image. The software defines "points of interest" from among the photos, or common points of high-contrast pixels. Next, the program pastes the images together seamlessly by matching up the points of interest. Much in the same way our two eyes work together to calculate depth, the software computes the distance and angle between two or more photos and lays the image over the model appropriately, creating a highly accurate 3D model that avoids the time intensive, "point by point" wireframe method. With Pix4D's 3D models, you can navigate in all directions as well as change the date on a timeline to see what a place looked like at different times of the year. The company is collaborating with several drone makers (including another EPFL startup,senseFly) to market their software as a package with senseFly's micro aerial vehicles, or autonomous drones. Pix4D's time element avoids waiting for Google to update its satellite data or for an expensive plane to fly by and take high-resolution photos. Farmers, for example, can now send relatively inexpensive flying drones into the air to take pictures as often as they like, allowing them to survey the evolution of their crops over large distances and long periods of time. And since the calculations are done on a cloud server, the client doesn't need a powerful computer of his or her own.

Engineers at Stevens Institute of Technology have developed a technique to optically modulate the frequency of a laser beam and create a signal that is disrupted significantly less by environmental factors, says Dr. Rainer Martini. The research provides for enhanced optical communications, allowing mobile units not tied to fiber optic cable to communicate in the range of 100 GHz and beyond, the equivalent of 100 gigabytes of data per second. Eventually, the team hopes to extend the reach into the terahertz spectrum. The frequency or amplitude modulation of middle infrared quantum cascade lasers has been limited by electronics, which are barely capable of accepting frequencies of up to 10 GHz by switching a signal on and off.  Marini and his team have developed a method to optically induce fast amplitude modulation in a quantum cascade laser to control the laser's intensity. Their amplitude modulation system employed a second laser to modulate the amplitude of the middle infrared laser, using light to control light. The current detector is only capable of detecting frequencies up to 10 GHz, but Dr. Martini is confident that a new detector will make the system capable of much higher frequencies. With an optical system that is stable enough, satellites may one day convert to laser technology, resulting in a more mobile military and super-sensitive scanners, as well as faster Internet for the masses, says Martini. Ref.: "Optically induced fast wavelength modulation in a quantum cascade laser," Applied Physics Letters, July 7, 2010.