Naval Research Lab Studies Solar Storms

By Bob Freeman, Special to American Forces Press Service

WASHINGTON - Imagine a threat to the global community with the potential to damage communication satellites, interrupt navigation systems, shut down regional power grids, impede oil and gas exploration, expose aircraft crews to high levels of radiation, and endanger the lives of astronauts.

That threat exists, but it's not from any well-organized terrorist group. It's from the sun.

"Ultraviolet and X-ray radiation and particle emissions from the sun affect the ionosphere and [the Earth's magnetic field] and can cause lots of problems to space and ground assets," explained Russell Howard, an astrophysicist at the Naval Research Laboratory, in a Dec. 21 interview on Pentagon Web Radio's audio webcast "Armed with Science: Research and Applications for the Modern Military."

Howard was joined in the interview by George Doschek, head of the Naval Research Laboratory's Solar Terrestrial Branch, who explained that the "solar wind," a stream of charged particles and radiation constantly blowing toward the Earth, is intensified by disturbances in the sun's magnetic field, such as sunspots, solar flares, and coronal mass ejections.

"All the activity on the sun is produced when the sun's magnetic field is converted into particle emissions and acceleration, and radiation," Doschek said. He explained that the magnetic field of the sun actually stores energy, which is released in bursts when the structure of the field suddenly changes to a configuration that holds less energy.

"When that happens," he said, "we think that the excess energy goes into radiation and accelerating particles."

Howard, who holds a doctorate in chemical physics, said the release of electromagnetic radiation in the form of X-rays, ultraviolet rays, and gamma rays, interacts with the Earth's ionosphere.

"The ionosphere is an electrically charged layer of the Earth's atmosphere," he said. "It's most important, because it reflects radio waves, and that's what allows us to propagate radio waves around the Earth," said Doschek, who holds a doctorate in physics. Radiation affects the ionized particles in the ionosphere, causing them to absorb radio waves, causing communication fade-outs, he explained.

"That's the issue of the satellites themselves," Howard said. "But with ionospheric disturbances, you are also getting an increase in electron density in certain areas, and this can cause failures in GPS." He added that there were about 30 minutes of complete GPS outage in December 2006.

In addition to GPS, Howard noted that the effects of solar storms on communications satellites extend to such things as cell phones, pagers, television, the Internet and streaming video. "Society is becoming increasingly dependent on space-based assets," he commented.

Howard added that strong ionospheric disturbances can also cause ground controllers to lose track of low orbit satellites. "Electromagnetic energy comes in and heats the atmosphere," he said. "When you heat the atmosphere, you get increased density at spacecraft altitude, and that causes an increase in drag, and you can lose track of them."

Solar radiation also can pose a threat to humans. "The radiation can damage astronauts, or if you're flying [in an aircraft] over the polar regions, you have to worry about getting too much radiation from X-rays and ultraviolet radiation," he said.

"The transpolar routes are becoming extremely popular for the airlines," Howard added, "so the crews have to wear radiation dosimeters to measure how much exposure they are getting."

High-energy particles also pose a hazard to anyone working high in the atmosphere or in space, Howard said. "Particles can also be released, and they're coming at fantastic speeds, 500 times that of a bullet, and their combined mass is a million times that of a Nimitz-class carrier," he explained.

"With a coronal mass ejection, you can get a billion tons of matter moving 1 million miles an hour toward the Earth," Doschek added. He noted that coronal mass ejections were first identified by researchers at NRL in 1971.

The solar wind interacts with the Earth's magnetic field, Doschek said. "When solar particles get into the magnetosphere, they're trapped there, and that's when they can do a lot of damage," he noted.

In a large solar storm, the particles also can damage equipment. "You can get energetic particles at hundreds of electron volts of energy, and these can damage electronics in our space assets," Howard said.

"They can cause electrical discharges inside the spacecraft and destroy the circuitry," Doschek added, "and they can cause disruptions in the software and communication links in the satellite until it has to be rebooted."

The solar wind can directly affect people on Earth, as well.

Howard described the impact of the solar wind on the Earth's magnetosphere as a force that puts pressure on the magnetic field. With large solar storms, the pressure intensifies and distorts the shape of the field.

"The magnetosphere, when it gets compressed, induces a current in the Earth's crust," he explained, "and power transmission lines can get a huge amount of back current into transformers that actually burns them up. I've seen pictures of copper straps that are two inches thick that are melted. It's just amazing."

A mass ejection in 1989 shut down the Quebec power grid, which is connected to power grids along the entire East Coast of the United States, Howard said. Quick action on the part of an engineer disconnected the Quebec grid from the other grids. "It was within seconds before it would have taken out the power for the entire northeast part of the U.S.," Howard said.

In addition to the loss of transformers, which cost about $10 million to replace, the disruption of power was estimated to be a loss of $2 billion of gross national product, he said.

These induced currents in the Earth's crust also can affect oil and gas exploration. Howard explained that oil prospecting often is done by trailing a magnetometer behind a ship to look for changes in the magnetic field structure. "A huge oil or gas deposit would be indicated by a change in the field properties," he said, "but if one of these storms comes along, you've completely lost that activity."

While it may not be possible to stop the solar storms, it would be useful to know when they are coming to better prepare for them. To do that, researchers need to have a better understanding of their nature, and NRL has been conducting solar research since 1946, Doschek said.

"We try to understand what is causing the atmosphere to do what it's doing," he said, "which means that we want to understand the mechanisms by which the sun's magnetic field, and the energy within that field, can be converted to particles."

Doschek explained that most solar research needs to be accomplished above the atmosphere, using remote sensing instruments carried on spacecraft.

"We use spectrometers," he said, "to determine the temperature and density, and even the motions within the sun's atmosphere. We have another instrument, called a coronagraph, which blocks out the main radiation from the sun and looks at the outer part of the atmosphere of the corona. With this instrument, we can see hot gases and coronal mass ejections as they come toward the Earth."

Reserachers have made some progress in developing notice of solar activity. "We have instruments that are actually on two NASA spacecraft that are in orbit around the sun, "Howard said. "It's called the STEREO mission. They're looking at the sun and the region between the sun and Earth from two different viewpoints."

Howard explained that these sensors, located more than 100 million miles from Earth, are able to observe solar activity as it happens and more precisely pinpoint the time the charged particles will reach the Earth. But not all solar events send high-pressure streams of dangerous particles towards the Earth.

"Part of our research is to determine the parameters that we need to be studying in order to say whether this will have a powerful impact on Earth or not," he noted.

Another approach to forecasting solar events is with the use of computer modeling. Doschek described three-dimensional numerical simulation models that attempt to portray how changes in the sun's magnetic field get converted into thermal energy based on complex circulations on the sun's surface, and observed phenomena like sunspots.

"The magnetic field is part of a dynamo," he explained, "and when sunspots appear -- these are regions of strong magnetic field -- they get fed into the model and the field moves around the sun."

From these models, the researchers have developed a predictive algorithm for the solar wind. "That works on the basis of how the magnetic field originates on the sun," Doschek said.

Howard acknowledged that the modeling effort is in the infant stages, but noted that the observations and measurements being made by space-based sensors are providing a foundation for improving the models.

"Hopefully, in 10 to 15, maybe 20 years, we'll be much better than we are today," he said.

(Bob Freeman works in the Office of the Oceanographer of the Navy.)

Endeavour Releases Naval Research Lab Sats

The Atmospheric Neutral Density Experiment 2 (ANDE-2) satellite suite designed by the Naval Research Laboratory is deployed from space shuttle Endeavour. The ANDE-2 suite consists of two spherical satellites to monitor atmospheric density and to improve methods for placing space objects in low Earth orbit. (Photo courtesy NASA/Released)

By Donna McKinney, Naval Research Laboratory Public Affairs

WASHINGTON (NNS) -- The Naval Research Laboratory's satellite suite, the Atmospheric Neutral Density Experiment 2 (ANDE-2), was deployed from NASA's Space Shuttle Endeavour July 30.

The ANDE-2 satellite suite consists of two nearly perfectly spherical micro-satellites with instrumentation to perform two interrelated mission objectives. The first objective is to monitor the total atmospheric density in order to improve methods of accurately tracking space objects. The second is to provide a test object for both radar and optical U.S. Space Surveillance Network sensors.

ANDE-2 is a low-cost mission designed to study the atmosphere of the Earth from low-Earth orbit by monitoring total atmospheric density between 300 and 400 km altitude. ANDE-2 data will be used to improve methods for tracking the orbit of space objects and to calibrate the Space Fence, a radar space surveillance system belonging to the Air Force 20th Space Control Squadron, a principal resource for tracking low-Earth orbiting space satellites.

Navy's ANDE-2 Launched Aboard Endeavour Downlink on 2 Meters

Blog Editor's Note: Want a shot at monitoring an orbiting spacecraft? Hams, Scanner Enthusiast and other radio hobbyist have a chance to monitor these two Navy satellites on their amateur band downlinks at 145.825 MHz. See AMSAT notice at the end of this post.

By Donna McKinney, Naval Research Laboratory Public Affairs

WASHINGTON (NNS) -- The Naval Research Laboratory's (NRL) satellite suite, the Atmospheric Neutral Density Experiment 2 (ANDE-2), launched aboard NASA's Space Shuttle Endeavour July 15.

The ANDE-2 satellite suite consists of two nearly perfectly spherical micro-satellites with instrumentation to perform two interrelated mission objectives. The first objective is to monitor the total atmospheric density along the orbit for improved orbit determination of resident space objects. The second objective is to provide a test object for both radar and optical U.S. Space Surveillance Network sensors.

ANDE-2 is a low-cost mission designed to study the atmosphere of the Earth from low-Earth orbit by monitoring total atmospheric density between 300 and 400 kilometer altitude. ANDE-2 data will be used to improve methods for the precision orbit determination of space objects and to calibrate the Space Fence, a radar space surveillance system belonging to the Air Force 20th Space Control Squadron, a principal resource for tracking low-Earth orbiting space satellites.

Because of ANDE-2's particular design requirements, a new deployment technique was developed by the Air Force Space Test Program and tested with the ANDE Risk Reduction (ANDERR) flight in December 2006. The primary ANDERR mission objective, a test of the Shuttle deployment mechanism, was successful.

The ANDE project was conceived and developed at NRL, by Andrew Nicholas of NRL's Space Science Division. The mission consists of two microsatellites with the same size but different masses sent into orbit at the same time: the lighter satellite, known as Pollux, and the heavier satellite, Castor.

The Castor spacecraft carries active instruments: a miniature wind and temperature spectrometer to measure atmospheric composition, cross-track winds and neutral temperature; a Global Positioning Sensor; a thermal monitoring system to monitor the temperature of the satellite; an electrostatic analyzer to monitor plasma density spacecraft charging.

Each satellite contains a small lightweight payload designed to determine the spin rate and orientation of the satellite from on-orbit measurements and from ground-based observations. The two microsatellites will slowly separate into lead-trail orbit to provide researchers an opportunity to study small-scale, spatial and temporal variations in drag associated with geomagnetic activity.

Both satellites will be fitted with an array of 30 retro reflectors and will be observed by the U.S. Space Surveillance Network and domestic and international satellite laser ranging sites. The variation in observed position will be used to determine in-track total density. Scientists will determine its position in relation to the passive satellite to compute total density and validate drag coefficient models. In addition, instrumentation on board Castor will measure density and composition.

A joint effort between the Space Science Division and the Naval Center for Space Technology to routinely process and analyze the ANDERR data has led to improved orbit determination and prediction using an atmospheric model correction method. The ANDE data provide a valuable tool for correcting deficiencies in atmospheric models and have led to advancements in miniature sensor technology. These advancements are pivotal for multi-point in-situ space weather sensing. The DoD Space Test Program will provide launch services for the ANDE-2 mission.

Experiment/Payload Description

Research Summary

Atmospheric Neutral Density Experiment - 2 (ANDE-2) objectives are to measure atmospheric density and composition in low Earth orbit (LEO) and to better characterize the parameters used to calculate a satellite's drag coefficient.

This experiment consists of two microsatellites, called ANDE Active (AA) spacecraft (Castor) and the ANDE Passive (AP) spacecraft (Pollux), that are launched from the Space Shuttle cargo bay.

These spherical satellites are 19 inches in diameter and will be tracked by the Satellite Laser Ranging systems and the Space Surveillance Network.

Description

The main objective of Atmospheric Neutral Density Experiment - 2 (ANDE-2) is to measure the total atmospheric density between 100 and 400 km. The density data that is gathered will be used to improve orbit determination calculations of the orbits of resident space objects.

ANDE-2 consists of two spherical micro satellites. These satellites are launched from the Space Shuttle cargo bay into a circular orbit just below the International Space Station altitude.

Both satellites will be tracked by the Satellite Laser Ranging (SLR) system and the U.S. Space Surveillance Network (SSN). These satellites have the same dimensions, but have different masses. Because of the difference in mass, the satellites will drift apart over time. Observing the satellites' position will provide a study on spatial and temporal variations in atmospheric drag associated with geomagnetic activity.

Operational Requirements

ANDE-2 uses two spherical microsatellites which are launched from the Space Shuttle cargo bay. Both satellites are 19 inch diameter spheres, have a mass of 50 and 25 kg, and are constructed of aluminum. The surface of both spheres contains an embedded array of sensors including 30 retro reflectors, six laser diodes for tracking, and six photovoltaic cells for determining orientation and spin rate. Both spheres also have thermal monitor systems. The ANDE spacecraft are located inside the Internal Cargo Unit (ICU). The ICU is made of three aluminum sections. Each section is separated by a light band separation system. Once ejected from the cargo bay, the ICU will separate and deploy the ANDE spheres at a safe distance from the shuttle.

Operational Protocols

ANDE will be launched from the Space Shuttle cargo bay. The two microsatellites will be contained inside the ICU canister. Once the ICU canister is a safe distance from the Space Shuttle, two micro satellites will be released at an altitude of approximately 350 km.

And from AMSAT

AMSAT News Service Bulletin 193.06
From AMSAT HQ SILVER SPRING, MD.
July 12, 2009
To All RADIO AMATEURS
BID: $ANS-193.06

Castor and Pollox, two satellites in the Atmospheric Neutral Density Experiment (ANDE) program are ready to fly with the launch of STS-127 from Kennedy Space Center. The ANDE mission consists of two spherical spacecraft fitted with retro-reflectors for satellite laser ranging (SLR). The constant and well-determined cross section and surface properties of the ANDE spacecraft provide an ideal set of objects for monitoring atmospheric drag and the calibration of space surveillance network (SSN) assets both radar and optical.

Castor
Castor is a 19 inch diameter aluminum sphere with a mass of 63 kg. It is as near perfect sphere as possible given the constraints of cost and manufacturability. The sphere is split in half with e delrin disc. The hemispheres are also the satellite antenna. For power, the satellite has 112 19AH lithium primary cells. This provides about 7000 watt-hours of power which has to last for the one year mission.

The satellite has several different types of sensors. There are two main sensors, a Neutral particle wind and temperature spectrometer and an ion mass spectrometer.

A group of college students designed and built a MEMS sensor payload to test some commercial gyroscopes and a magnetometer. There are also six light sensors and six temperature sensors mounted in the satellite hemispheres.

Pollox
The Pollux satellite was originally to be a passive satellite with retroreflectors for laser ranging. It has been turned into a high school student project involving several schools in the Fairfax County, Virginia area.

The satellite is powered by twenty-eight 19AH Lithium-ion cells configured to provide 14 volts. The battery configuration uses the spare ANDE satellite hardware.

The electronics is based on cubesat hardware developed at the Naval Research Laboratory and Stensat Group LLC.

The communications board contains the transmitter and receiver. The transmitter operates at 2 meters and can put out up to 1 watt of signal. Power level is adjustable. The transmitter can operate at 1200 baud AFSK and 9600 baud FSK. The transmitter uses the AX.25 protocol. An experimental FX.25 protocol will be tested that adds forward error correction capability to the AX.25 protocol and still allows typical TNCs to decode the packets.

Both satellites will transmit on 145.825 MHz. Additional details about the telemetry format, as well as the FX.25 and GMSK experiments can be found at https://goby.nrl.navy.mil/ANDE/Main.html