Satellites Flying In Formation To Help Improve Understanding Of Earth

Satellites Flying In Formation To Help Improve Understanding Of Earth

ScienceDaily (Dec. 5, 2008) — Based on the outstanding success of the first tandem mission between ERS-2 and Envisat last year, ESA has paired the two satellites together again to help improve our understanding of the planet.

ERS-2, ESA’s veteran spacecraft, and Envisat, the largest environmental satellite ever built, both carry Synthetic Aperture Radar (SAR) instruments that provide high resolution images of the Earth's surface.

By combining two or more SAR images of the same site, slight alterations that may have occurred between acquisitions can be detected. This technique, known as SAR interferometry or InSAR, has proven to be very useful for applications such as glacier monitoring, surface deformation detection and terrain mapping.

ESA engineers configured the first SAR tandem mission, which took place from September 2007 to February 2008, and the current one, which began on 23 November, to ensure that the satellites both acquire data over the same area just 28 minutes apart.

This short time separation allows for changes that occur quickly to be detected. Fast-moving glaciers, for instance, move more than 200 m per year and can move as much as 1 cm in 30 minutes. The ability to detect these small changes occurring on the ground between acquisitions is also allowing scientists to understand better and improve the quality of the SAR interferometry technique.

The current tandem mission, scheduled to run until 27 January 2009, is continuing the work of the first tandem mission with respect to measuring the velocity of fast-moving glaciers, detecting land-ice motion and developing elevation models over flat terrain.

However, based on the first mission’s proven ability to provide precise elevation information over flat regions, data from the current mission will also be used to identify natural carbon sources and sinks in Kazakh Steppe and wetlands in permafrost regions.

A challenging configuration

ESA engineers had to overcome many challenges in order to put Envisat and ERS-2 into a tandem flight configuration. For instance, in 2001 ERS-2 lost the ability to be manoeuvred in the usual way by onboard gyroscopes, navigational tools that allow mission controllers to maintain the correct position of satellites.

The operational lifetime of satellite missions is normally determined by the functioning of onboard gyroscopes. Without them, the ESA team had to work out a way of positioning the spacecraft by operating onboard sensors in a new way.

Part of their creative solution involved using a device called the Digital Earth Sensor (DES), which is designed to provide the horizon line to allow basic checks on the spacecraft’s position, and analysing Doppler frequency shifts in the signals of ERS-2’s radar instruments.

ERS-2, launched in 1995, and Envisat, launched in 2002, have exceeded the time they were intended to stay in orbit. Since they remain operational and continue to provide quality data about our planet, engineers are trying to use as little fuel as possible so as not to shorten their lifetimes.

"The strategy is to align the tandem start date with an Envisat manoeuvre. Therefore, there is no need to spend extra hydrazine for Envisat. For ERS, the manoeuvre to place it in tandem position is such that the satellite drifts back to its nominal orbit without additional manoeuvre after the tandem campaign," ESA Mission Planner Manager Sergio Vazzana said.

WEATHER NOTE

StormZone Simulation 2008

The Miami-Dade County Department of Emergency Management & Homeland Security (DEM&HS) recently hosted approximately 60 students and teachers from South Dade Senior High School in Homestead and Eugenia E. Thomas Middle School in Doral to participate in a simulated activation of the County's Emergency Operations Center (EOC).

The students, who are involved in a magnet program to study emergency management, role-played elected officials, emergency management coordinators and other key personnel during a fictional Category 3 hurricane that struck Miami-Dade. Three DEM&HS coordinators assisted the students during the exercise. The simulation was coordinated by StormZone, a Miami-based non-profit organization that teaches emergency management to middle and high school students.

Historic September (KLOT) Flooding – Lessons Learned

A series of heavy rain events, partially caused by the remnants of three tropical storms, produced serious and widespread flooding across northern Illinois and northwest Indiana in September.

The first heavy rain occurred on September 4 and 5 when remnants of hurricane Gustav brought two to four inches of rain to the region. Because of dry conditions through much of August, this rain didn’t cause any significant flooding. However, it saturated the ground, increased flows on area streams, and set the stage for more serious flooding later in the month. Moisture from a Pacific tropical storm, Lowell, moved along a stationary front producing a wave of heavy rain across northern Illinois and northwest Indiana on the 13^th.

This was followed by a second wave of heavy rain on the 14^th, as the remnants of Hurricane Ike moved up from Texas. Rainfall totals on September 13 and 14 were 7 to 11 inches, with the heaviest totals in Lake and Porter Counties in northwest Indiana. The total September rainfall for the area was 12 to 16 inches.

The image shows rainfall across the entire Midwest from September 12-15, 2008. This image is courtesy the Midwestern Regional Climate Center in Champaign, IL.

The result of the heavy rain was widespread flooding of roads, creeks, drainage areas, open fields, low lying areas and basements. Small streams such as the North Branch of the Chicago River, Salt Creek, the DuPage River, the Little Calumet River and its tributaries rapidly rose to record or near record levels. These small streams fed larger rivers including the Des Plaines, Fox, Kankakee, and Illinois Rivers. The Des Plaines reached the second highest crest on record at Des Plaines and Riverside, while the Illinois set records at Morris and LaSalle.

Flooding in downtown Des Plaines. Photo courtesy of CLTV.

Flooding at O'Hare International Airport.

Despite two significant tornado outbreaks, on January 7 and June 7, and an intense wind and tornado event on August 4, the flooding of mid September was by far the biggest weather event in the Chicago area for 2008. This event impacted more people and resulted in more damage and fatalities than any event in this area in the last several years. Total estimated damages from the flooding are around 100 million dollars. There were four flood related fatalities, making this the most deadly storm-related weather event in northern Illinois and northwest Indiana since eight people were killed by a tornado in Utica in April, 2004.

Flooding on the Illinois River at Peru.

Historically, about half of all flood fatalities occur in vehicles, when people drive into flooded roads, or get swept off a road by fast moving water. While there were several incidents where people in vehicles were swept away by flood water and had to be rescued, none of the four fatalities in the September flooding occurred in vehicles. Hundreds of cars were also stranded in deep standing water, fortunately with no loss of life. Here is a review of the four fatalities;

· A 28 year old man drowned in a retention pond in Arlington Heights.

· An 83 year old man drowned in a flooded window well at his home in Oak Lawn.

· A 48 year old man and 78 year old man drowned trying to save a boy in a flooded culvert in Chesterton, IN. The boy survived.

Our sympathies go out to the families.

Lessons learned;

· Everyone should have a hazardous weather plan – at home, at work, and at school. The plan should encompass all hazards, not just tornadoes. Chicago area weather hazards include flooding, lightning, damaging wind and large hail, extremes of heat and cold, and winter storms. Make sure everyone in your care is familiar with the plan. Practice the plan by conducting periodic drills.

· A key part of any hazardous weather plan is to have a reliable method of receiving watches, warnings and other weather information. One of the best methods is to use a NOAA Weather Radio. For more information click here; http://www.crh.noaa.gov/lot/?n=nwr

· Heed warnings. A flash flood warning means heavy rain will lead to rapid flooding of roads, creeks, small streams, drainage areas, low lying areas, and basements. Stay home. Remove valuables from basements and flood-prone areas before the flood.

· Do not drive through flooded roads, especially if the water is flowing swiftly. Even heavy pickups and SUVs with four wheel drive can be swept away by fast moving water that is only one to two feet deep. Turn Around, Don’t Drown! For more information, visit http://tadd.weather.gov/

· Do not let children play near flooded creeks, ditches, or drainage retention ponds. Fast moving water that is only ankle deep can sweep a child away. Victims can be pinned against grates or storm drains by powerful currents.

· Do not swim, wade, or boat in flooded areas. In addition to the potential for drowning, flood water may be contaminated by oil from roadways, chemicals from farm fields, and backup from overflowing storm sewers. Sometimes flood swollen streams are tempting to adventurers in canoes and kayaks, but these streams can be extremely dangerous.

· Do not venture into flooded basements unless power to the building is shut off. There may be an electrical hazard.

Record flooding along the Illinois River at Morris. Photo by Don Lyon.

Finally, the National Weather Service would like to thank everyone involved in the flood event.

· Volunteer weather spotters, amateur radio operators, Cooperative observers, and other volunteers who measure and report rainfall and storm reports.

· State, county, and local government agencies including emergency management, police, fire, and public works/highway departments.

· Partners in the broadcast media, who help disseminate the watches and warnings and keep the public informed.

· Print media, whose news stories provide much of the information that goes into the final StormData publication.

· School administrators who insist on developing sensible, comprehensive hazardous weather plans and conduct periodic drills.

· People who head the warnings and encourage family, neighbors, and coworkers to also take precautions

Have a happy and SAFE holiday season, and rest assured that the men and women at your National Weather Service office in Romeoville are on guard 24/7, watching out for you.

The National Weather Service office in Romeoville has completed the StormData summary of the September flooding in northern Illinois and northwest Indiana. StormData is a monthly publication that documents all hazardous weather occurrences. It is available online at http://www.crh.noaa.gov/lot/?n=stormdata.

MARITIME NOTE

Issues You Should Be Aware of on Travel Safety

Travelling is always a fun experience as you get to explore a lot of new destinations and take part in various activities. In fact there is countless number of people on the surface of the earth who consider travelling to be their favourite hobby and go out exploring new places whenever they get time. There are some other people who need to travel a lot not because they are fond of it but they have some professional requirements.

Travelling with family or for education are other two important reasons why people do travel extensively. Whatever be the reason for your travel, you need to extremely careful about the safety while you are not at the home town. The foreign places can at times be very risky. Accidents, robberies and disease are the reasons why you need to take adequate safety measures while travelling.

If you are a frequent flyer and is not aware of the precautions and steps that you need to take while an air journey the n this is time to charge up yourself with all the mishaps that can take place in the sky. Before you board a plane you should make sure that the airlines you have chosen to fly with is a reputed one. This is important because the general ones often do not have ample safety arrangements for their passengers.

They do not carry adequate number of oxygen masks, life jackets and life belts. This is the reason why at the time of any emergency they are not able to help you out. In fact you need to be careful about your health conditions as any negligence can take your life. If you feel that as you are travelling by a ship or a train, you do not need to take care of the travel safety arrangements than you are quite wrong. Because accidents can take place anytime and anywhere.

There are other safety measures that you need to take in order to make sure that you travel safely. If you are going for international tours then never forget to fetch enough information about the rules and restrictions of that country. This will help you to keep away from many unwanted troubles. If this is the first time you are visiting the place then a travel agency can be of help to you.

Always make sure that you have a travel insurance that will cover all sorts of medical expenses abroad. You should be extremely careful about the identity documents you are carrying like the passport and visa loosing which can land you up in jail as this is a criminal offence to intrude into a foreign country without official proof. So be conscious about your safety while going for a tour.

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