The United States National Academies of Sciences, Engineering, and Medicine 2017 Earth Decadal Survey recommended a new NASA “Designated” program element to address a set of five high-value Targeted Observables during the next decadal period. In response to that recommendation, and based on guidance from NASA’s Earth Science Division, a team has been formed to perform an architecture study associated with the Surface Deformation and Change (SDC) Targeted Observable. Surface deformation measurements are critical for studies related to earthquakes, volcanoes, landslides, and changes in groundwater levels and corresponding subsidence or uplift, as well as measuring ice sheet and glacial stability and their contributions to sea level rise, permafrost thaw, surface change. The Decadal Survey report recognizes this criticality for its Earth Surface and Interior objectives, and also for a number of Hydrology and Climatology objectives, identifying twenty-three surface deformation-related objectives throughout the report.

While the Decadal Report Surface Deformation and Change Targeted Observable is focused on surface geodesy (i.e. change in position of the surface), NASA has directed that the scope of the study include some architectures that intrinsically support research- and applications-grade measurements of observables such as soil moisture, vegetation structure, disturbance, agricultural monitoring, wetlands processes, coastal processes, ocean processes, sea ice hazards monitoring (e.g. icebergs and polar sea-lane variability). Based on this, the SDC architecture study will explore architectures that are optimized for phase-based geodetic performance and architectures that also support amplitude-based radiometrically accurate imagery. A science and applications traceability matrix (SATM) has been developed for this expanded set of geophysical observables and is online for public comments.

SDC’s observational requirements for many of these objectives cover a number of performance parameters such as spatial resolution, deformation precision and repeat interval. In reaching its final recommendation on a cost-effective strategy for the SDC observable, the Decadal Survey Committee presumed that the measurement implementation will involve Synthetic Aperture Radar (SAR) and Interferometric SAR (InSAR) technologies. The Decadal Survey references the NASA-ISRO SAR (NISAR) Mission design performance of 12-day repeat interferometry, and calls for shorter repeat cycle (sub-weekly to daily), potentially at the expense of spatial resolution if necessary to stay within the recommended development cost.

The SDC Study has three main objectives: 1) Identify and characterize a diverse set of observing architectures, including innovative observing systems that can disrupt the norm for interferometric SAR observations; 2) Assess the ability of each of the architectures to meet SDC objectives, including cost effectiveness; 3) Perform sufficient in-depth design study of one selected architecture to enable initiation of a Phase A concept study. To accomplish these objectives, the study team is engaging US national expertise in Earth Science research, applications, technology, mission formulation and implementation. The team comprises NASA centers with relevant expertise and is engaging the international community, government, academia, and industry.

The SDC architecture study will examine the research and applications benefits of the data sets derived from these existing and planned systems, which may be complicated by different data access modalities for various satellites, ranging from free and open data to commercial but restricted data sets. In this study, we are working with other agencies (space agencies and data sponsors), and commercial providers to understand and quantitatively assess the ways in which the variety of data can be applied to scientific research and other applications. The study team has developed a simulation tool to quantitatively assess the performance of the existing and planned SAR constellations, which will be considered as an observing system. This will allow research and applications community members to gain a more quantitative understanding of the critical gaps in our observations from the government Programs of Record and the commercial sector that NASA must fill to meet the SDC science and application objectives.

The results generated from the simulation tool and the SATM parameters form the inputs to the value framework (VF). The VF assesses the benefits, costs, and risks of each architecture for the science and applications communities, as captured in the Decadal Survey. The needs of the applications community are documented in a study report focusing on the entire value chain of non-research, Earth observation data users. The study found that the applications community will also benefit from an interferometric SAR with ~10m resolution, global coverage, and multi-polarization data with a weekly sampling plan collected over a decadal time frame. Some community members also expressed interest in multi-band observations. A community assessment report is being developed expanding this initial study.

In summary, the SDC Study commenced in October 2018 and is planned to run for five years. In the initial two years, community needs were collected and parsed into the SATM. Technology readiness and partnerships opportunities were assessed, and about forty architectures were identified. These architectures are now being evaluated against the needs, and a down-selection will be conducted this year using the value framework. The remaining time will be spent in more detailed studies of the down-selected architectures, with a final down-selection and report at the end in preparation for mission implementation. In this paper, we will describe the status of the study and how potential partners can become involved.

The National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) are both developing future L-band SAR missions to address key science questions and application needs relevant to solid Earth, ecosystems, cryosphere, and hydrology. The NASA-ISRO SAR (NISAR) mission is a dual-frequency L-/S-band SAR satellite scheduled for launch in late 2023 and recently identified as a pathfinder for the NASA Earth System Observatory. NISAR will acquire global dual-polarimetric L-band data with 20 MHz range bandwidth every 12 days (6 days ascending and descending), delivering unprecedented dense time-series at L-band and new Geocoded Single Look Complex products. The Radar Observation System for Europe at L-band (ROSE-L) is one of the ESA’s High-Priority Candidate Missions scheduled for launch after 2028 with the goal of augmenting the Copernicus constellation to address important information gaps and enhance existing Copernicus services and related applications. In the current design, ROSE-L is a two-spacecraft system that will operate in the Sentinel-1 orbit and be phased to achieve a repeat interval of 6 days.

Both NISAR and ROSE-L are designed to make repeated observations from a narrow orbital tube in order to generate time-series with nominal zero interferometric baselines. While this design choice has several benefits, it cannot address some of the measurements recommended by the 2017-2027 Decadal Survey for Earth Science and Applications. Two of these measurements are (1) 3D surface deformation vector and (2) vegetation vertical structure, for which long along-track and cross-track baselines, respectively, are required. NASA has been conducting dedicated studies to develop science and application traceability matrices (SATMs) as well as identify technology gaps and candidate architectures for Surface Deformation and Change (SDC) and Surface Topography and Vegetation (STV) measurements. The question is whether diverse science needs with potentially competing system requirements can be met more easily by coordinating international efforts for future SAR mission development.

This paper discusses concepts involving satellites flying in formation with satellites such as NISAR and ROSE-L in order to augment the observation capabilities of these missions through denser coverage, multi-squint or multi-baseline measurements. Additional satellites spaced in time in the same orbital plane as NISAR or ROSE-L can improve the temporal sampling density of each. Receive-only co-fliers are attractive thanks to their simplified hardware architecture and to the ability to coherently combine their images without relying on a tight cooperation with the mothership SAR satellite. The talk addresses challenges and opportunities of proposed free- and co-flier concepts for NISAR and ROSE-L by leveraging previous ESA’s SAOCOM-CS studies and current NASA’s SDC and DARTS IIP efforts in the context of on-going international collaborations between NASA and ESA.

Session: B6.01 National EO satellite missions


Building upon RADARSAT-1 heritage, RADARSAT-2 was launched in 2007 with added beam modes and polarizations that helped develop new operational applications and increased SAR data consumption within the Government of Canada by a factor of five (5). Launched in June 2019, the RADARSAT Constellation Mission (RCM) aims to ensure continuity of operational SAR imagery for RADARSAT-2 users, as well drawing from the constellation approach to enable new applications. Now more than one year of operations, the RCM is becoming the Canadian Government’s premier mission to provide all-weather day and night data in support of Canadian sovereignty and security, environmental monitoring, natural resources management and other government priorities such as Northern development. As a three-satellite constellation, it can cover most of Canada and its surrounding waters on a daily basis. Compared to previous RADARSAT missions, coverage increases significantly in Canada’s North, for example providing coverage of the Northwest Passage three to four times daily. With the increased frequency of revisit, emerging applications such as measurement of land deformation and operational disaster management can be further exploited.

The RCM is designed to respond to core needs, which at the highest level can be summarized as:
• Daily coverage of Canada's territorial and adjacent waters for maritime surveillance, including ship detection and monitoring of ice, marine wind, and oil pollution; and,
• Monitoring of all of Canada for disaster mitigation on a regular basis (monthly to twice-weekly) to assess risks and damage-prone areas; and,
• Regular coverage of Canada's land mass and inland waters, up to several times weekly in critical periods, for resource and ecosystem monitoring.

Introduction

In order to ensure the Italian leading role in the remote sensing sector, The Italian Space Agency intends to promote in the next years several technology developments in both active and passive space born sensors (through the acquisition of capabilities in new frequency bands as well as the process of miniaturization in traditional bands), the development of radar programs, such as COSMO-SkyMed Second Generation (CSG), GEOSAR (in collaboration with the Russian Federation space agency), PLATiNO-1 and P-Band.
To this aim several Italian industries will sustain and develop technologies associated with the PLATiNO, whose 1st mission will be deployed in 2022, mini multi-purpose standard platform which will be capable of embarking a whole range of payloads covering a wide set of programmatic sectors (such as those relating to Telecommunications, Earth Observation and Exploration just to name some) in scientific or applicative field. In a similar way several other initiatives will start in the course of this year including the development of missions and technologies for nano-satellites up to 25 kg.

COSMO-SkyMed Second Generation
The CSG program, started in 2009 in cooperation with the Ministry of Defense, guarantees to Italy a dual national infrastructure for "all-weather, 24/7 " satellite observation of the Earth. The deployment of the Second Generation of COSMO-SkyMed represents a technological leap in terms of performances and operational life of the system and consequently provides Italy with a leadership role at world level in the Earth Observation sector with SAR technologies. The first CSG satellite was launched in December 2019 while the launch of the second one is scheduled in January 2022. In the next few years the constellation will therefore be completed with the development of the following third and fourth.

GEOSAR
A joint Italian-Russian technical-scientific geosynchronous SAR Mission feasibility study is currently underway. The GEOSAR system is planned to be based on the use of the geosynchronous orbit for SAR applications. This highly innovative concept allows obtaining a new capacity complementary to the assets currently deployed in LEO, guaranteeing therefore a continuous availability of data in selected areas, allowing particularly promising applications in the field of monitoring and emergency management, agriculture, natural resources and meteorology.

PLATiNO-1
PLATiNO 1 will be the first mission using the multi-purpose, high-performance PLATiNO minisatellite platform. For the first Mission, the Agency will develop a compact radar for both bistatic and monostatic operation, with sub-meter resolution, in order to fill the growing market segment of low-cost compact SAR instruments for future constellations. The payload capitalizes what has been developed in Italy to date in the field of X-band SAR technology.
With a development phase started in 2017 the project is now completing the phaseC and its launch is planned by end of 2022.