Tag Archive for: Satellite

Meteorologists are eager to protect the spectrum from radio frequency interference coming from satellite mega-constellations threat.

At the American Meteorological Society (AMS) annual meeting in Denver, meteorologists and spectrum experts expressed concern about proposals for SpaceX’s second-generation Starlink broadband constellations and acknowledged that other proposed mega-constellations could create interference as well.

SpaceX enquired to the U.S. Federal Communications Commission for a license to transmit signals from gateway stations to nearly 30,000 Starlink second-generation constellations in the 81 to 86 gigahertz band.

“The sheer number of potential gateway uplink stations around the world could contribute to adjacent band contamination and further due diligence would be needed,” said David Lubar, Aerospace Corp. senior project leader, said at the AMS meeting. “We do not know if their out-of-band emissions will be an area of concern.”

Meteorologists pick up faint signals indicating humidity over land in the 86 to 92 gigahertz band, adjacent to the bands Starlink has proposed for uplinks.

It’s not yet clear whether the Starlink uplinks would pose any danger to the meteorological observations, but weather forecasts rely on passive radiometers to pick up faint signals to identify water vapor, precipitation and atmospheric temperature in various spectral bands.

“These bands are established by the fundamental laws of physics,” Tony McNally, principal scientist in the European Centre for Medium-Range Weather Forecasts Research Department, said at the AMS meeting.

Complicating the matter is the fact that “the signals that we are looking for with our passive satellites are much smaller than the interference patterns created by some of the other uses of the spectrum,” McNally added. “I would liken it to trying to gaze up at the stars at night when someone puts an incredibly bright flashlight in your eyes.”

Meteorologists sought protection from unwanted emissions in the 81-86 gigahertz band at the 2019 World Radiocommunications Conference in Egypt. At the time, the International Telecommunications Union body of delegates declined to take up the matter.

As a result, the FCC has no current regulations that would limit SpaceX’s use of the band.

“Any new international rules are unlikely to be enacted until after 2027,” Lubar said.

This is just one example of the whack-a-mole predicament meteorologists face in trying to safeguard atmospheric measurements and weather data relays from RF interference.

Another potential problem relates to the passive measurements meteorologists make from 50.2 to 50.4 gigahertz. Careful observation of that band reveals temperatures at various levels of the atmosphere. That data, paired with humidity measurements in the 180 to 184 gigahertz band, are key elements of weather forecasts.

Existing regulations protect the 50.2 to 50.4 gigahertz band from interference, but the signals are so weak they could be drowned out by noise emitted in adjacent bands.

“These systems in space are measuring extremely sensitive bits of energy,” said Beau Backus, Johns Hopkins Applied Physics Laboratory senior spectrum manager. “That makes it essential that this be in protected areas.”

Tens of thousands of satellites are expected to launch in the next decade. Many satellite operators are proposing transmitting data to spacecraft in bands immediately above and below the 50.2 to 50.4 gigahertz band.

“The industry is moving faster than our scientific development,” Michael Farrar, director of the National Centers for Environmental Prediction at the National Weather Service, said at the AMS meeting. “This problem is going to accelerate. We should build a process that can rapidly respond to these scenarios.”

The American Meteorological Society’s RF Allocation Committee also is concerned about potential interference in the 23 to 24-gigahertz band, where the Advanced Technology Microwave Sounder on the National Oceanic and Atmospheric Administration’s Joint Polar Satellite System collects passive measurements of atmospheric water vapor. Those observations combined with data from other active and passive sensors on U.S. and international satellites help meteorologists predict storm tracks and rainfall levels.

“Our systems are making very good use of combinations of channels,” McNally said. “The problem with it is that if you then have a losing battle [to protect] one channel, you can effectively wipe out the value of channels which are not contaminated because you don’t have this corroborating piece of evidence from the channel that you’ve lost. The quality of forecasts that we enjoy in our society are a result of this very sophisticated multichannel usage in data simulation systems.”

Lockheed Martin has developed a satellite-based augmentation system that leverages both GPS and Europe’s Galileo

Lockheed Martin’s vice president of navigation systems, Andre Trotter said that the availability of a new GPS navigation signal for civilian users is creating market opportunities in so-called satellite-based augmentation systems (SBAS) that countries around the world are developing or upgrading to support transportation and other industries.

Six GPS 3 satellites that broadcast the L1C signal have been launched since 2018, the most recent one last week. GPS 3 is a modernized version of the U.S. military’s Global Positioning System satellites that broadcast positioning, navigation and timing signals. Compared to earlier generations, the GPS 3 satellites provide military users extra protection from jamming attacks but one of its most significant features is the L1C signal for civilian users that is interoperable with Europe’s Galileo navigation satellites.

Lockheed Martin has built 10 GPS 3 satellites under a 2008 contract from the U.S. Air Force, and will produce at least 10 more GPS 3F, a more advanced version.

“The company developed what it calls a 2nd generation SBAS that takes advantage of both GPS L1/L5 and Galileo E1/E5 signals to provide more accurate navigation and positioning, and reduce dependence on any one system,” Trotter told SpaceNews.

Lockheed Martin in September won a $1.18 billion 19-year contract to develop and operate the Southern Positioning Augmentation Network (SouthPAN) for the governments of Australia and New Zealand. The system is expected to be operational by 2028. “There is a significant amount of testing that must go on in order for the signals to be certified for different types of use, whether that be safety-of-life or commercial aircraft operations,” Trotter said.

Lockheed Martin’s SBAS broadcasts on two frequencies to augment signals from GPS and Galileo. 

“We are currently broadcasting the dual-frequency multiple constellation SBAS signal as part of SouthPAN,” Trotter said. “As additional GPS 3 and GPS 3F satellites are launched, service will improve even further.”

Winning the SouthPAN contract “could lead to more opportunities, as we have the ability to expand this enabling technology globally,” he said. “We are having discussions with other potential international customers. We also expect that more benefits will be realized as we bring in users and learn about new applications of the technology.” 

The SouthPAN system, for example, will improve accuracy from the current 5 to 10 meters, to about 10 centimeters, he said. More precise navigation and positioning data, Trotter said, is in high demand for commercial aviation, precision agriculture, maritime tracking, and the operation of drones and unmanned vehicles.

The U.S. SBAS is known as the Wide Area Augmentation System (WAAS). Europe’s is called EGNOS, or European Geostationary Navigation Overlay Service. Several countries have implemented SBAS systems, including Japan and India, and more are in development. 

In the SouthPAN system, an SBAS payload is hosted on an Inmarsat geostationary Earth orbit communications satellite, which rebroadcasts the augmentation messages to user receivers. Lockheed Martin operates a tracking, telemetry and control ground station in Uralla, New South Wales. Spain-based GMV will develop SouthPAN’s data processing and control centers.

According to research, combining satellite technology with machine learning may allow scientists to better track and prepare for climate-induced natural hazards.

During the past century, many natural phenomena like hurricanes, snowstorms, floods and wildfires have grown in intensity and frequency.

While humans can’t prevent these disasters from occurring, the rapidly increasing number of satellites that orbit the Earth from space offers a greater opportunity to monitor their evolution, said C.K Shum, co-author of the study and a professor at the Byrd Polar Research Center and in earth sciences at The Ohio State University. He said that potentially allowing people in the area to make informed decisions could improve the effectiveness of local disaster response and management.

“Predicting the future is a pretty difficult task, but by using remote sensing and machine learning, our research aims to help create a system that will be able to monitor these climate-induced hazards in a manner that enables a timely and informed disaster response,” said Shum.

Shum’s research uses geodesy—the science of measuring the planet’s size, shape and orientation in space—to study phenomena related to global climate change.

Using geodetic data gathered from various space agency satellites, researchers conducted several case studies to test whether a mix of remote sensing and deep machine learning analytics could accurately monitor abrupt weather episodes, including floods, droughts and storm surges in some areas of the world.

In one experiment, the team used these methods to determine if radar signals from Earth’s Global Navigation Satellite System (GNSS), which were reflected over the ocean and received by GNSS receivers located at towns offshore in the Gulf of Mexico, could be used to track hurricane evolution by measuring rising sea levels after landfall. Between 2020 and 2021, the team studied how seven storms, such as Hurricane Hana and Hurricane Delta, affected coastal sea levels before they made landfall in the Gulf of Mexico. By monitoring these complex changes, they found a positive correlation between higher sea levels and how intense the storm surges were.

The data they used was collected by NASA and the German Aerospace Center’s Gravity Recovery And Climate Experiment (GRACE) mission, and its successor, GRACE Follow-On. Both satellites have been used to monitor changes in Earth’s mass over the past two decades, but so far, have only been able to view the planet from a little more than 400 miles up. But using deep machine learning analytics, Shum’s team was able to reduce this resolution to about 15 miles, effectively improving society’s ability to monitor natural hazards.

“Taking advantage of deep machine learning means having to condition the algorithm to continuously learn from various data inputs to achieve the goal you want to accomplish,” Shum said. In this instance, satellites allowed researchers to quantify the path and evolution of two Category 4 Atlantic hurricane-induced storm surges during their landfalls over Texas and Louisiana, Hurricane Harvey in August 2017 and Hurricane Laura in August 2020, respectively.

Accurate measurements of these natural hazards could one day help improve hurricane forecasting, said Shum. But in the short term, Shum would like to see countries and organizations make their satellite data more readily available to scientists, as projects that rely on deep machine learning often need large amounts of wide-ranging data to help make accurate forecasts.

“Many of these novel satellite techniques require time and effort to process massive amounts of accurate data,” said Shum. “If researchers have access to more resources, we’ll be able to potentially develop technologies to better prepare people to adapt, as well as allow disaster management agencies to improve their response to intense and frequent climate-induced natural hazards.”

The latest version of the ESPA ring arrays experiments but also more advanced operational smallsats

A ring-shaped satellite carrier the U.S. Air Force developed a decade ago to arrange experiments has evolved into a reliable asset to get small national security payloads to geosynchronous Earth orbit. 

The ESPA ring which is short for Evolved Expendable Launch Vehicle (EELV) Secondary Payload Adapter, was created to fill unused capacity on national security space rockets. The newest version of the ring designed by Northrop Grumman, the Long Duration Propulsive ESPA or LDPE, deploys experiments but also more advanced operational smallsats.

Each ring has six ports that can accommodate 320 kilograms of payload mass per port.

“LDPE provides added propulsion, power, and avionics subsystems enabling operations as a fully functional satellite,” Space Systems Command program manager Lt. Col. Michael Rupp, said in a news release.

Under a contract with U.S. Space Systems Command, Northrop Grumman built three LDPE rings for national security missions. One launched in December 2021, the second in November 2022 and the third one will fly on a SpaceX Falcon Heavy in the upcoming USSF-67 mission. A more advanced version of the ring is in the works under a July 2022 $22 million contract.

Space Systems Command said all payloads on LDPE-1 and LDPE-2 were successfully deployed to geostationary orbits. 

The original ESPA ring started as a joint development by the Air Force Research Laboratory and Orbital Sciences back in 2012, said Troy Brashear, Northrop Grumman vice president of national security systems. Orbital Sciences was later acquired by Northrop Grumman.

Military customers are seeing the utility of the ESPA ring as a much more affordable option than dedicated launches, and the rings are flexible enough that payloads can be swapped at the 11th hour, Brashear told SpaceNews

“An interesting part of this satellite program is the ability to make changes on the fly,” he said. That is not possible with most space missions where the payloads are designed for specific interfaces and substitutions are difficult to make. “On LDPE we’ve been able to show that payloads on any of the six ports can be swapped out as late as at the launch site.”

Northrop Grumman manufactures the ESPA satellites in Gilbert, Arizona. After being shipped to Cape Canaveral, individual payloads in recent missions were changed out right before launch, he said. “And it provided a ton of flexibility to the customer.” 

A sort of resilience

Brashear said the ability to add a new payload to the mission on short notice is increasingly important as a form of resilience, giving the Space Force options to deploy experiments or operational satellites in response to emerging needs. 

“The foreign threat environment is changing pretty fast. And for our customers, speed and agility to stay ahead of those challenges is paramount,” he said. “This program is providing that sort of resilient architecture to put things into orbit faster, and cheaper since it’s a very small satellite structure, utilizing empty space on a ride that would go unused.”

The LDPE satellites fly to geostationary orbit on big rockets that typically carry a large primary payload and the ring as a secondary payload. When it reaches orbit, the LDPE is released from the second stage. Once the ring is deployed, the individual payloads can stay attached to the platform permanently or can be dispensed as independent satellites, go off and do their own missions.

“The U.S. government’s investment over the last 10 years in these ESPA products has just timed up very nicely with the threat environment,” he said. “If these investments hadn’t been made 10 years ago, we wouldn’t have this freight train to space where we can take six payloads up in a cost-effective manner.”

Another benefit of these rings is that they are interchangeable with any of the national security space rockets the Space Force uses, which are operated by United Launch Alliance and SpaceX. LDPE have launched on ULA’s Atlas 5 and on SpaceX Falcon Heavy. “There are obviously different loads and dynamics and testing,” said Brashear. “But both ULA and SpaceX have been fantastic to work with.”