Friday, April 10, 2009

Scientists pinpoint the 'edge of space'

Where does space begin? Scientists at the University of Calgary have created a new instrument that is able to track the transition between the relatively gentle winds of Earth's atmosphere and the more violent flows of charged particles in space - flows that can reach speeds well over 1000 km/hr. And they have accomplished this in unprecedented detail.

Data received from the U of C-designed instrument sent to space on a NASA launch from Alaska about two years ago was able to help pinpoint the so-called edge of space: the boundary between the Earth's atmosphere and outer space.

With that data, U of C scientists confirmed that space begins 118 km above Earth and the results were published this week in the Journal of Geophysical Research.

The instrument - called the Supra-Thermal Ion Imager - was carried by the JOULE-II rocket on Jan. 19, 2007. It travelled to an altitude of about 200 kilometers above sea level and collected data for the five minutes it was moving through the "edge of space."

The Canadian Space Agency invested $422,000 in the development of the Supra-Thermal Ion Imager instrument on JOULE-II.

The ability to gather data in that area is significant because it's very difficult to make measurements in this region, which is too high for balloons and too low for satellites.

"It's only the second time that direct measurements of charged particle flows have been made in this region, and the first time all the ingredients - such as the upper atmospheric winds - have been included," says David Knudsen, associate professor in the Department of Physics and Astronomy at the University of Calgary. ...

"When you drag a heavy object over a surface, the interface becomes hot. In JOULE-II we were able to measure directly two regions being dragged past each other, one being the ionosphere -- being driven by flows in space -- and the other the earth's atmosphere," says Knudsen, who also is the head of the Space Physics Division of the Institute for Space Imaging Sciences (ISIS). The institute is a research partnership between the University of Calgary and University of Lethbridge.

The measurements confirmed what other scientists consider the boundary or edge of space.

... The paper "Rocket-based measurements of ion velocity, neutral wind, and electric field in the collisional transition region of the auroral ionosphere" was published this week in the Journal of Geophysical Research. It can be found on-line at

via Scientists pinpoint the 'edge of space'.

This confirms that space is 387,139 feet (73 miles ) up. Here is a related story from Poker Flat AK (SPX) Jan 24, 2007:

From Poker Flat Research Range north of Fairbanks, four NASA rockets launched into an aurora display over northern Alaska, starting at 3:29 a.m. Alaska Standard Time. Scientists hope to learn more about electrical heating of the thin atmosphere from about 60 to 120 miles above Earth's surface with the launch of these rockets. The project is called JOULE II. Staff at Poker Flat Research Range coordinated with the Federal Aviation Administration to ensure that airspace was secure before launching all rockets. Each rocket's flight lasted about 12 minutes, and all rockets performed as planned, flying to their desired locations in space, with precision greater than 95 percent.

Miguel Larsen, a professor at Clemson University, was the principal investigator for JOULE II, which consisted of two Terrier Orions, a Black Brant V, and a Black Brant IX. The rockets launched in two pairs--the pairs consisted of one rocket with instruments to read the detailed structure of the electrical currents within the aurora, while a second rocket released a visible tracer of trimethyl aluminum vapor to measure the winds and turbulence at that altitude range.

Using sensitive digital and film cameras, scientists watching from Poker Flat, Coldfoot, and Fort Yukon determined how winds in the upper atmosphere contorted the visible tracer. They will use the information to track the winds in the aurora region.

The two releases of trimethyl aluminum produced a milky white glow when exposed to oxygen in the upper atmosphere, and may have been visible over parts of Alaska. -

Joule II comprised several different experiments using several different rockets.

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