SOCON—Sustained Ocean Color Observations Using Nanosatellites (Invited Presentation)

The Sustained Ocean Colour Observations from Nanosatellites (SOCON) project is a PUBLIC/PRIVATE/FEDERAL partnership funded by Gordon and Betty Moore Foundation for development and “proof-of-concept” for a low-cost, miniaturized multispectral ocean color imager (HawkEye) capable of flight on a CubeSat (SeaHawk). The University of North Carolina Wilmington (UNCW) has contracted with Cloudland Instruments, LLC, to construct the HawkEye Coastal Ocean Color Imager and Clyde Space, Ltd., to build the SeaHawk satellite bus and Spaceflight, Inc, to handle launch services. The group have entered into a U. S. Space Act Agreement with the NASA Science Mission Directorate to expand free access to the data. The data from SOCON will have direct and significant relevance to many of international programs and in helping meet many of international science objectives and could have a large impact in helping address a number of critical societal needs, especially in the highly variable coastal regions of the world. The sensor will have the capability of collection of 8 color bands and be designed with a form factor to fit into a custom 3U (i.e., 10 X 10 X 30 cm) CubeSat; have spatial resolution of 120 m and swath of 230 km in a 575 km LEO orbit. The sensor data will be integrated into NASA’s Ocean Data Processing System (ODPS) and supported by their SeaWiFS Data Analysis System (SeaDAS) analysis package that will be distributed worldwide by the NASA Ocean Biology Distributed Active Archive Center (OB.DAAC) at the Goddard Space Flight Center. Under our Intellectual Property Terms, the data will publicly available as soon as possible at no cost, and all reasonable actions necessary to ensure the details of the sensor design are made freely available in a manner that is sufficient to enable another competent individual or organization to replicate the HawkEye Ocean Color Sensor and Seahawk CubeSat

The mission will demonstrate ocean colour observation in high temporal and spatial resolution modes, through the use of a miniature ocean colour sensor, HawkEye, flown aboard a CubeSat. The final product will be 130 times smaller (10-cm × 10-cm × 30-cm), 45 times lighter (4.7 kg), with a ground resolution that’s eight times better (120 meters versus 1 km), while still having a Signal/Noise Ratio approximately 50 percent that of SeaWiFS, the satellite sensor that originally set the bar for ocean color imaging. SeaHawk is the CubeSat that shows that you can deliver performance comparable to traditional spacecraft at a fraction of the cost and development time.

The HawkEye Coastal Ocean Color Sensor is designed to capture an image of the oceans and land with 120-meter per pixel resolution from a 540 km nominal orbit. Each image will have dimensions of 1800x 6000 pixels, 8 bands deep. The bands are similar to those used by the SeaWiFS instrument. The instrument is of push-broom design, with 4 linear array CCDs, each containing 3 rows of detectors, sweeping the field of view as the satellite passes overhead. The instrument is designed to not saturate on either the land or clouds using a technique called bi-

linear gain. The ground swath imaged will be 230 x 720 km in extent. (The optical design and characteristics are discussed in another paper in this session by Alan Holmes of Cloudland Instruments).

The SeaHawk platforms are pushing the boundaries of what was previously thought to be possible with such tiny spacecraft. The most obvious challenge throughout the design is the extremely tight physical limitations for both the payload design and CubeSat platform. The requirement to collect data each orbit places a large power demand on the satellite. These challenging requirements will be met using a range of Clyde Space advanced subsystems including: the highly efficient Third Generation FlexU EPS, high-performance solar panels and a

30Wh lithium polymer battery. SeaHawk will generate an immense amount of data (around 1.1

Gigabits for the full observation sweep). In order to maximize the availability of the SeaHawk data, the Clyde Space platform will make use of an X-Band communications system which will deliver a high data rate downlink to the NASA Near Earth Network (NEN), where the data will be sent directly to NASA/GSFC for processing and distribution. To support image geolocation, the spacecraft includes a Global Positioning System (GPS) receiver, high-accuracy Sun sensors and rate gyros.

Successful demonstration of the SeaHawk mission will be ground breaking for both the nanosatellite and Ocean Colour communities and will prove the ability of CubeSats to achieve high-resolution optical performance, in turn enabling high-quality science missions.

The program has contracted with Spaceflight, Inc, for launch services to handle the logistics for SeaHawk-1 to launch in 2018 aboard a SpaceX Falcon 9 from Vandenberg Air Force Base. The second SeaHawk-2 is estimated to launch in early 2019. SeaHawk-1 is currently scheduled to be launched into a 575km LEO orbit 1st Q 1018 with SeaHawk-2 scheduled for 1-year later 1st Q

2019, allowing for a 6-8 month overlap when both will be in orbit. Data will become available as the satellites finish their commissioning phases and enter their operational phases with data available internationally via the OB.DAAC.