NASA’s EMIT Mission Taps FPGA Processing to Measure Surface Minerals
Representing a joint effort to accurately characterize the minerals present on the Earth’s surface, NASA’s JPL leverages optical and FPGA-based advances to help in modeling the Earth’s climate.
In an effort to give climate scientists a better understanding of our planet’s dust-forming minerals, NASA’s Earth Surface Mineral Dust Source Investigation (EMIT) mission leverages advanced technologies from a broad range of manufacturers to help characterize the movement of small dust particles.
With the mission’s first measurements coming in near the end of July, the mission’s onboard electronics set a new precedent for high-performance data processing and storage in harsh environments such as space, including FPGA-based computing.
The EMIT instrument plays a key role in modeling the transport of small dust particles and their impact on the Earth’s climate. Image used courtesy of NASA JPL
In this article, an overview of the EMIT mission is given alongside some of the key contributions that allow for mineral characterization from the International Space Station (ISS). In addition, the future goals of the EMIT mission will be discussed in relation to the mission’s motivations and current achievements.
Measurements from the Comfort of Space
Climate science in general relies on measurements to be taken at a global level. While local anecdotal evidence can often launch some discussion, the Earth cannot be parsed into individual closed climates with no impact on each other.
In the case motivating the EMIT mission, dust particles originating from arid regions can be blown by strong winds thousands of miles away, creating changes in local climates. As such, a worldwide measurement technique must be employed to obtain comprehensive data to allow climate scientists to fully understand the sources of climate change.
To tackle the global measurement problem, NASA’s Jet Propulsion Laboratory worked alongside other companies to develop the EMIT instrument. At its core, EMIT combines traditional imaging with spectrometry to determine the mineral content at the surface of the earth. With traditional imaging, at each point in the image, only the visible wavelengths reflected by the object are shown.
With the EMIT instrument, however, each point in the image contains a spectrum of wavelengths that may be used to determine the mineral content at that point in the image, helping scientists to quantify the potential origins or destinations for key dust particles that may be affecting local climates.
An image of the EMIT instrument functional block diagram, illustrating the overall approach to characterizing the minerals present on the surface of the Earth. Image used courtesy of NASA JPL
The EMIT instrument is currently mounted onboard the ISS, where it is actively taking and processing measurements, then storing them temporarily so that they may be transmitted back to the ground. Since the instrument is attached to the space station moving at 17,500 mph, a clever design technique is employed to reduce the computational requirements.
To keep the design simple, the EMIT device only takes measurements in a single dimension perpendicular to the motion of the ISS. Despite this, the forward motion allows for repeated measurements to be “stitched” together, creating an image while only needing to process one column at a time.
Measuring the Spectrum One Column at a Time
In order to measure the spectrum created by different minerals, the EMIT instrument relies on sophisticated optical, electrical, and mechanical components from numerous agencies. Sunlight reflected from the Earth’s surface is focused using a mirror-based and is directed to the spectrometer.
It is then passed through a Dyson block and diffraction grating to separate the incident light into its spectral components. The light may then be sorted and detected using an order sorting filter and detector array. The optical components were developed by Arizona Optical Systems, Optimax, Viavi Solutions, and Teledyne Imaging Sensors.
An image of the EMIT system with and without the outer panels. The system consists of optical and electrical components to create and characterize the received spectrum. Image used courtesy of NASA JPL
After hitting the detector array, the light’s energy is converted to a weak analog signal. This signal is then amplified and digitized before being fed into a high-performance FPGA for digital signal processing. The EMIT’s FPGA board design is based on a standard Alpha Data COTS (commercial off-the-shelf) Zynq7100 board in an XMC form factor.
After processing the signals, the data is compressed and stored to be downlinked from the ISS. The electrical and mechanical components were developed by Alpha Data, Mercury Systems, Northrop Grumman, and Sierra Lobo.
Working in Space to Understand the Earth
Despite the fact that the ISS circles the Earth once every 90 minutes, the EMIT instrument will likely take a considerable amount of time to produce reliable and comprehensive measurements due to cloud cover or other obfuscations. Once the measurements are reasonably complete, however, climate scientists will have a new tool to use in their modeling and understanding of the Earth’s climate
In addition, the innovation made by Alpha Data in their Zynq7100 FPGA is expected to be transferable to future projects where high-performance data processing or downlink is required, making the EMIT project a benefit to climate scientists and designers looking to build reliable space-proven systems.