Featured Research

from universities, journals, and other organizations

Radio telescope, GPS use ionosphere to detect nuclear tests

Date:
February 19, 2013
Source:
Naval Research Laboratory
Summary:
Analyzing radio telescope interferometry and GPS data recorded of the ionosphere, scientists are able to detect acoustic-gravity waves from surface and underground nuclear explosions.

For each source observed near and after the Hunters Trophy event, maps of TEC gradient fluctuation power as a function of east-west and north-south spatial frequency. Here, the peak spectral power over all temporal frequencies is shown as an image in each panel with contours representing the mean power over all temporal frequencies. The range in azimuths expected for waves propagating from Hunters Trophy for altitudes between 100 and 900 km is shown in each panel with black lines.
Credit: U.S. Naval Research Laboratory

U.S. Naval Research Laboratory radio astronomer, Joseph Helmboldt, Ph.D., and researchers at Ohio State University Department of Civil, Environmental, and Geodetic Engineering analyzed radio telescope interferometry and Global Positioning Satellite (GPS) data recorded of the ionosphere during one of the last underground nuclear explosions (UNEs) in the U.S., codenamed Hunters Trophy.

Related Articles


Situated in the Plains of San Agustin, 50 miles west of Socorro, New Mexico, twenty-seven 25-meter parabolic dish antennas collectively make up the National Radio Astronomy Observatory's Very Large Array (VLA) radio telescope.

The VLA is an interferometer, meaning it operates by multiplying the data from each pair of telescopes together to form interference patterns. The structure of those interference patterns, and how they change with time as Earth rotates, reflect the structure of radio sources in the sky.

Designed as a radio synthesis telescope, observing bands between 1 and 50 gigahertz (GHz), the VLA is chiefly used to observe cosmic sources. While such observations require detailed calibration schemes to remove the effects of the ionosphere, this calibration data is seldom used to actually study the ionosphere.

During the Hunters Trophy event at the Nevada Test Site, Sept. 18, 1992, the VLA was observing a series of relatively bright cosmic sources at 1.4 GHz and positioned in a compact D-configuration, allowing an increased sensitivity to smaller-scale fluctuations. The data for these observations were retrieved from the VLA archives and self-calibration was performed using each source to obtain differences in total electron content (ΔTEC) time series for each antenna.

"One can see that between roughly 20 and 25 minutes after the UNE, the signature of disturbances in the ionosphere moving toward the northeast and southwest are nearly perpendicular to the direction from Hunters Trophy," said Helmboldt. "Given their characteristics, it seems likely that these disturbances are associated with small-scale distortions propagating along the larger traveling ionospheric disturbance generated by the Hunters Trophy explosion."

GPS can also contribute to detection and discrimination of UNEs. GPS signals are sensitive to ionospheric disturbance, and this phenomenon can be used to further validate concurrent VLA measurements. By studying the ionosphere, namely Traveling Ionospheric Disturbances (TIDs) excited by acoustic-gravity waves from surface and underground explosions, the magnitude of the fluctuations greatly increased roughly 30 minutes after detonation -- consistent with GPS-derived propagation speed. The travel time and the travel distance of each event are highly correlated.

"Combining the results of both spectral techniques, we found a class of intermediate and small-scale waves," said Helmboldt. "Our exploration of VHF/UHF observations with the VLA has successfully demonstrated the power of this instrument to characterize a variety of transient ionospheric phenomena."

The resolution of the VLA is set by the size of the array -- up to 36 km (22 miles) across. At its highest frequency (43 GHz) a resolution of 0.04 arcseconds is achieved -- sufficient to see a golf ball being held 150 km (100 miles) away.


Story Source:

The above story is based on materials provided by Naval Research Laboratory. Note: Materials may be edited for content and length.


Cite This Page:

Naval Research Laboratory. "Radio telescope, GPS use ionosphere to detect nuclear tests." ScienceDaily. ScienceDaily, 19 February 2013. <www.sciencedaily.com/releases/2013/02/130219140510.htm>.
Naval Research Laboratory. (2013, February 19). Radio telescope, GPS use ionosphere to detect nuclear tests. ScienceDaily. Retrieved November 29, 2014 from www.sciencedaily.com/releases/2013/02/130219140510.htm
Naval Research Laboratory. "Radio telescope, GPS use ionosphere to detect nuclear tests." ScienceDaily. www.sciencedaily.com/releases/2013/02/130219140510.htm (accessed November 29, 2014).

Share This


More From ScienceDaily



More Space & Time News

Saturday, November 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Scientists Find Invisible Space Shield Protecting Earth

Scientists Find Invisible Space Shield Protecting Earth

Newsy (Nov. 27, 2014) An invisible barrier is keeping dangerous super fast electrons from interfering with our atmosphere, but scientists aren't entirely sure how. Video provided by Newsy
Powered by NewsLook.com
NASA's First 3-D Printer In Space Creates Its First Object

NASA's First 3-D Printer In Space Creates Its First Object

Newsy (Nov. 26, 2014) The International Space Station is now using a proof-of-concept 3D printer to test additive printing in a weightless, isolated environment. Video provided by Newsy
Powered by NewsLook.com
Feast Your Eyes: Lamb Chop Sent Into Space from UK

Feast Your Eyes: Lamb Chop Sent Into Space from UK

Reuters - Light News Video Online (Nov. 25, 2014) Take a stab at this -- stunt video shows a lamb chop's journey from an east London restaurant over 30 kilometers into space. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Soyuz Spacecraft Docks With International Space Station: NASA

Soyuz Spacecraft Docks With International Space Station: NASA

AFP (Nov. 24, 2014) A Russian Soyuz spacecraft carrying Italy's first female astronaut safely docks with the International Space Station, according to NASA. Duration: 00:40 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins