In a relatively short time, Spire has grown from a small start-up company to the largest commercial producer of satellite-based GNSS Earth observation products. As of May 2020, and after 21 satellite deployments, Spire now has over 80, 3U (10x10x10 cm) Cubesats satellites operating in a variety of orbit planes, third only to Planet and SpaceX in the size of its satellite constellation and growing with each launch. Spire satellites host three primary payloads: a dual-frequency GNSS science receiver, an automatic identification system (AIS) receiver for ship tracking, and an automatic dependent surveillance—broadcast (ADS–B) receiver for aircraft tracking. The Earth observations produced with Spire’s GNSS science receiver include atmospheric profiles performed by radio occultation (RO), space weather observations (slant total electron content (TEC) and scintillation indices), and GNSS reflectometry (GNSS-R) using signals from the GPS, GLONASS, QZSS, and Galileo constellations. Spire was the first commercial company to produce RO observations and has participated in a number of commercial data pilot programs with NOAA, NASA, USAF, and ESA, Over the past few years, Spire has expanded and matured the Earth observation products available and has continued to improve and grow the size and capabilities of its constellation.
Spire now produces thousands of low-latency RO profiles and millions of TEC observations each day, with plans for over 100 RO-producing satellites in the full constellation. Additionally, Spire recently added GNSS-R capabilities by launching the first two GNSS-R scatterometer configuration satelliites in December of 2019, with plans for two more GNSS-R satellites to be launched in mid-2020. Due to its agility and rapid launch cycle, averaging launches of four to eight satellites every six weeks, Spire has the unique ability to improve performance and add capabilities on-orbit that are impossible with traditional, risk-averse satellite missions. Spire has provided RO and space weather data to the second NOAA Commercial Weather Data Pilot program, the US Air Force Commercial Weather Data Pilot program, ESA, and numerous NWP centers and research institutions. Spire is also pioneering the provision of Earth observation data to NASA and ESA researchers through unique data purchase programs.
In our talk we will present an overview of the status and capabilities of the Spire satellites and describe the collection of GNSS-based Earth observations using the GPS, GLONASS, Galileo, and QZSS constellations. We will additionally outline our plans for expanding and adding products to the Spire Earth observation constellation.
Spire Global operates the world’s largest and rapidly growing constellation of CubeSats performing GNSS based science and Earth observation. The Spire constellation, performs a variety of GNSS science, including radio occultation (GNSS-RO), ionosphere and space weather measurements, and precise orbit determination. In December 2019, Spire launched two new satellites to perform GNSS reflectometry (GNSS-R), with plans for two more GNSS-R satellites to be launched in mid-2020. Due to its agility and rapid launch cycle, averaging launches of four to eight satellites every six weeks, Spire has the unique ability to improve performance and add capabilities on-orbit that are impossible with traditional, risk-averse satellite missions.
GNSS-R is a relatively new technique based on a passive bistatic radar system. The potential of space-borne GNSS-R observations for ocean and land applications has been demonstrated by other GNSS-R missions, including the NASA Cyclone Global Navigation Satellite System (CYGNSS) and the UK’s Technology Demonstration Satellite, TechDemoSat (TDS-1).
We present initial results from these new Spire GNSS-R satellites that are primarily focused on retrieving soil moisture but also estimate other Earth surface properties such as ocean wind speeds and flood inundation/wetland mapping. Prior to the launch of Spire’s GNSS-R satellites and in preparation for Level-2 data production, we developed algorithms and processing chains for land applications. We will present Spire's soil moisture retrieval method using CYGNSS observations. We evaluated the implemented soil moisture change detection algorithm by comparing the Spire’s daily soil moisture product with NASA’s Soil Moisture Active Passive (SMAP) observations and in-situ soil moisture measurements. The results of study indicate remarkable retrieval skills of the GNSS-R technique for soil moisture monitoring at a medium spatial resolution. Spire’s GNSS-R satellites are tuned for land applications with a series of hardware and software optimizations for better signal calibration and acquiring many more data per satellite compared to CYGNSS. A more robust GNSS-R soil moisture retrieval at finer spatial resolution will be possible in the near future after having more Spire satellites in orbit.
Spire’s current and future GNSS-R satellites will provide unprecedented sub-daily global coverage and fine spatial resolution. Such intensive data acquisition is of great importance for many land and ocean applications.
Spire Global, Inc. operates a large and rapidly growing constellation of CubeSats performing GNSS-based science and Earth observation. In a few short years, Spire has grown from a modest CubeSat kickstarter campaign to a paradigm-shifting provider of satellite data to NOAA, NASA, and other customers of Earth observations. Spire specializes in using science-quality observations of GNSS signals (e.g., GPS, GLONASS, Galileo, QZSS, etc.) to derive valuable information about the Earth environment. Currently, these observations include radio occultations to profile the neutral atmosphere with high accuracy and vertical resolution for applications such as NWP assimilation and climate monitoring, as well as to measure ionosphere slant total electron content and scintillation indices for space weather applications. As of May 2020, and after 21 deployments, Spire now has over 80, 3U Cubesats satellites capable of performing a variety of GNSS science, with plans to grow the constellation to well over 100 operational and continuously replenished satellites. Beginning in 2018, Spire began an effort to design and build the first of many GNSS bistatic radar (or GNSS-R) missions for Earth observations for a variety of applications, including soil moisture measurement, wetlands and flood inundation mapping, sea surface roughness and winds, and sea ice characterization. Following an agile model of rapid, iterative satellite development that has been refined over a few years to produce radio occultation payloads optimized for operation on ultra-small, 3U CubeSats, we adopted a very aggressive schedule to adapt the current Spire 3U bus and STRATOS GNSS science receiver to perform GNSS-R measurements, with a launch of satellites in December of 2019, and plans for two more GNSS-R satellites to be launched in 2020. We will discuss the goals and accomplishments of the Spire GNSS-R mission, the design and operational modes of the first batches of Spire GNSS-R satellites, and plans for a full, operational constellation of GNSS-R satellites. The Spire GNSS-R effort also has a parallel path that is already harnessing existing orbiting Spire satellites used for radio occultation to additionally perform grazing angle GNSS-R measurements for high-precision, phase-delay altimetry. This presentation will additionally discuss the unique experience of adapting the current constellation of radio occultation satellites to perform these new and valuable grazing angle GNSS-R Earth observations. We will introduce the concept of phase-delay altimetry and its potential to estimate surface heights on the order of 10 cm using observations of coherent GNSS signals reflected from various Earth surfaces. We will also show sea ice products derived from these new observations. Finally, we will discuss Spire’s potential to rapidly proceed with these measurements from research to operations and to make them available as a new set of Earth observations.
A low cost, low power, and low mass GNSS receiver (called Cion) has been developed and is currently flying on the CICERO cubesats. The receiver was designed in less than a year by JPL for Tyvak and GeoOptics for use in the GeoOptics CICERO constellation and leverages 25 years of JPL GNSS receiver design experience. Cion uses a commercial off-the-shelf (COTS) computer along with existing space qualified RF down-converters, software, and firmware to produce atmospheric Radio Occultation (RO) data. By combining a FPGA with dual core ARM processor and an embedded system controller, the Xilinx Zynq processor is an enabling technology that provides a customizable digital signal processing platform integrated into the computer (System on a chip) and enables off-the-shelf hardware to become the main engine behind this software defined radio. Using Linux for the on-board computer allows for fast development times and liberal use of existing open source software libraries. The parts of the receiver that require real-time implementation are performed in the Field Programmable Gate Array (FPGA), which can also be reprogrammed in flight. While the Zynq is not rad hard, the silicon on insulator (SOI) technology is rad tolerant 'by accident', allowing for its use in many space-based applications. Early results show that the Cion is working as designed, has demonstrated the first known GLONASS occultations, and obtains high quality atmospheric profiles with excellent lower troposphere penetration (near Earth’s surface).