Set of next-generation radar receivers to provide scientists with improved meteorological data
Global Navigation Satellite System (NGRx) Bistatic Radar Receiver
An SMD-sponsored team is developing a new radar receiver that will allow future space instruments to process more signals and produce data at much higher resolution, greatly improving scientists’ ability to study storms, observe polar ice, forecast floods and measure the height of the sea surface.
Severe hurricanes cost coastal communities around the world millions of dollars and thousands of lives each year. Knowing more about these complex storm systems would allow researchers to improve predictive weather models and predict severe storms with greater ease.
“We can’t control severe weather, but we can minimize their impact on human populations by giving people more time to prepare,” said Christopher Ruf, professor of climate and space science at the University. University of Michigan, Ann Arbor.
Ruf, who is also the principal investigator for NASA’s Cyclone Global Navigation Satellite System (CYGNSS) mission, has already developed a small constellation of micro-satellites that helps scientists measure wind speed over Earth’s oceans. Now, with support from NASA’s Earth Science Technology Office, Ruf wants to develop a new bistatic radar receiver that will dramatically increase the quality of data collected by future CYGNSS satellites.
“These satellites have been a valuable asset to scientists looking to study not only cyclones, but also things like soil moisture near the surface and the extent of microplastic debris in the ocean. This new receiver will make future CYGNSS system components even more valuable to Earth scientists,” Ruf said.
A Pegasus XL rocket brought the first payload of CYGNSS instruments to low Earth orbit (LEO) in 2016. Spaced about 12 minutes apart, these eight small satellites use signals from existing GPS instruments to observe the Earth by scattermetry. While most scatterometer instruments feature both a transmitter and a receiver, CYGNSS satellites take advantage of existing radar signals to reduce the overall complexity and cost of operating in space.
“Scattermetry uses a transmitter to transmit radar signals to the Earth’s surface and a receiver to determine the strength with which these transmitted signals reflect from Earth back into space. In a single set of instruments, this payload becomes quite heavy. By harnessing transmitted radar signals produced by GPS satellites already in orbit, we can remove the transmitter component from our instruments and continue to produce excellent data,” Ruf said.
But there is room for improvement. CYGNSS satellites currently orbiting the Earth can only process four transmission signals at a time, which limits their accuracy. Additionally, CYGNSS satellites can only process L1 signals, which are transmitted at a frequency of 1575.42 MHz. This negatively impacts the horizontal and vertical resolution of the collected data, making it difficult to use CYGNSS to study phenomena such as ice thickness and polar ice extent.
“CYGNSS has performed remarkably well in recent years, but as we expand its mission to include more scientific areas, we will need to improve certain components of these instruments,” Ruf said.
Its next-generation Global Navigation Satellite System (NGRx) bistatic radar receiver would do just that, increasing the scientific utility of CYGNSS instruments for studying complex Earth systems. Instead of processing only four L1 radar signals from the GPS satellites, future instruments equipped with this receiver could process up to fourteen L1 and L5 radar signals from the GPS and Galileo satellites.
“As a direct result of these changes, horizontal resolution will be improved by a factor of three, vertical resolution will be improved by a factor of ten, and spatial coverage by a factor of at least two, possibly even four,” Ruf said.
This improved resolution will allow researchers to better study storms, more clearly observe the extent of polar ice, develop better models for predicting floods, and even measure the sea surface at a level of detail that surpasses current CYGNSS instruments by a factor of ten.
“Having these capabilities on board small, cost-effective satellites is quite incredible. We will be able to produce great science at a much lower cost,” Ruf said.
NASA’s Earth Science Technology Office’s Instrument Incubation Program (IIP) is dedicated to helping researchers like Ruf develop their instrument concepts into fully functional sensors. Specifically, the IIP provided Ruf with critical funding and expertise for the development of its next-generation radar receiver.
Although the bistatic radar receiver is not quite ready to venture into space, it is ready for major flight testing. Partnership with the New Zealand Ministry of Business, Innovation and Employment; the New Zealand Space Agency; Air New Zealand; and the University of Auckland; Ruf plans to attach a prototype of his sensor to a Bombardier Q300 airliner. Ruf’s sensor will collect ocean data as the plane flies over New Zealand, helping his team determine if the instrument is ready for space applications.
“We are delighted to be working with our New Zealand colleagues to prepare this radar receiver for space. Taking something that was just an idea and developing it into a working prototype has been very satisfying, and we’re excited to send this instrument into space one day soon,” said Ruf.
Christopher Ruf, University of Michigan, Ann Arbor
Division of Earth Sciences Instrument Incubation Program
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