Carbonite video demonstration missions of SSTL on microsatellites
SSTL Carbonite series of platforms have an integrated avionics structure for fast manufacture in high volumes. They offer: 1)
• High resolution 1 meter GSD imagery from a 500 km orbit
• Agile platform ±45º off pointing
• Compatible with sun-sychronous and low inclination orbits
• Custom telescope with COTS camera adapted for space use
• Our Deep Thought avionics suite for user defined onboard processing and improved payload mass fraction
• Automated LEOP and in orbit commissioning to minimize time from launch to operational capability
• 5 year satellite design lifetime
• Mass optimized to increase single launch capacity
Fast revisits and system responsiveness enables applications including tracking and monitoring, change detection, Pattern of Life assessments and support to humanitarian or disaster operations.
Video imaging has a range of possible civil, security and commercial applications, but limitations in capability have previously made it difficult to implement operationally useful systems. There have been a few demonstrations of video imaging capability most notable on the TUBSAT series of missions, and more recently from the space station by Urthecast (Ref. 6).
Video imaging is generally only of interest if the resolution is good enough. For most applications this means that very high resolution (metric scale or better) is required. This poses challenges on the spacecraft in terms of instrument size, platform attitude stability, and geolocation.
Also, most applications for video require regular revisit to a particular location. Daily opportunities are probably a minimum requirement, and multiple opportunities per day support a much wider range of applications. As such constellations of satellites become essential in any video imaging system implementation.
Carbonite-1 is a technology demonstration microsatellite mission of SSTL , designed to demonstrate rapid-build techniques and to test COTS components and new avionics in orbit.
In 2014, based on earlier studies, SSTL decided to build a prototype, very low cost, high resolution satellite as an in-house technology demonstrator mission. This would become the leading satellite in a new class of in-orbit demonstrator missions aimed at trialing new advanced concepts for use in future missions. 2)
To keep costs to a minimum and to make use of an existing launch opportunity, the satellite had to be developed and built in six months. The decision to start was taken on the 1st July 2014 and the satellite manufacture was completed on 12th January 2015. This was followed by nearly two months of environmental testing, with the satellite ready to launch within eight months from start.
Merits of DMC3 and Carbonite: The DMC3 and Carbonite series of spacecraft are two sides of the same coin: one provides high fidelity imagery and the other provides high utility; but they both provide high resolution imagery. DMC3 is designed to provide high precision pointing capability with fast slewing in order to acquire multiple targets within a single pass. The images captured provide a high degree of precision with respect to the scene being captured. This enables the continuation of many of the commercial applications that have already been established which include: agriculture, deforestation, land use, and disaster monitoring.
The Carbonite series of spacecraft provide high utility by reducing the cost of entry for new and existing business models which includes the deployment of super-constellations. The addition of video capability from a large constellation can lead to new use cases which include persistent monitoring of regional hot spots for change detection. By reducing the cost and schedule per satellite, the Carbonite series can enable these super-constellations thereby providing a unique ability for sub-daily accesses. It will also enable new opportunities and bolster the capabilities of DMC3 type missions by providing higher revisit at a lower cost. This has the potential of disrupting the market by opening up new service areas with new applications that require a high revisit frequency, supplemented with high fidelity imagery, by providing data at a lower cost.
To achieve the challenging schedule and price targets, the satellite design is based on five key principles:
• Image quality to be "good enough" for the intended application
• Single string (except for the receivers that are hot redundant)
• Extensive use of COTS components, including in the imager
• Simple, non-optimized structure
• Use of existing technical solutions whenever possible.
The project organization was based around a very small core team of 5 engineers, substantially increasing decision speed. The team was given full autonomy to decide and implement the best solutions, within the wide boundaries set by the business.
The SSTL-X50 platform builds on three decades of experience at SSTL to realize a low-cost satellite bus for a wide range of missions, satisfying the lifetime requirements for Earth Observation and LEO communications operators. The main difference is the structure is built around the telescope using central shear walls made of milled aluminum. The avionics equipment was mounted to the shear walls around the imager. The closure and solar panels were made of sandwiched honeycomb panels.The size of the SSTL-X50 platform is 65 x 65 x 72 cm.
Figure 1: Photo of Carbonite-1 during AIT (image credit: SSTL)
The camera is based on a CMOS detector and provides color imagery with a GSD (Ground Sample Distance) of 1.5 m at an altitude of 650 km. The satellite can generate still images or videos of the area of interest. By flying the satellite at a lower altitude the GSD can be improved to 1 m.
Launch: The Carbonite-1 satellite was launched as a secondary payload on 10 July 2015 (16:28:00 UTC) on the PSLV-C28 (XL configuration) of ISRO from SDSC (Satish Dhawan Space Center) SHAR, located on the south-east coast of India. 3) 4) 5)
The primary payload on this mission was the three- spacecraft DMC-3 constellation of SSTL.
Orbit: Sun-synchronous orbit, altitude of 651 km, inclination of 97.8º LTAN (Local Time on Ascending Node) = 10:30 hours.
• CBNT-1 (Carbonite-1), a technology demonstration Earth Observation (EO) microsatellite (90 kg) of SSTL. Validation of some new avionics and EO capabilities.
• DeOrbitSail, a demonstration nanosatellite (7 kg) of SSC (Surrey Space Center).
With a total launch mass of 1440 kg, this represents the heaviest commercial launch so far for the organization. ISRO has built a circular Launcher adapter (L-adapter) and a triangular deck called Multiple Satellite Adapter-Version 2 (MSA-V2) exclusively for the purpose (Ref. 4).
• October 2018: Carbonite-1 is still operational after three years, and is sharing its groundstation passes with other commercial satellites operated by SSTL. The satellite is still being used to test out new improved AOCS and imaging techniques and to build heritage on the payload equipment (Ref. 6).
- At the end of the mission, the de-orbit sail on the platform will be deployed in-order to reduce the altitude and orbital lifetime to within 25 years.
Figure 2: Top: Raw Carbonite-1 strip image of Walnut Ridge, USA, Bottom: Strip image of Dubai, UAE, acquired in 2016 (Ref. 2)
Carbonite-2 (Pathfinder mission for Vivid-i constellation)
Carbonite-2 is a technology demonstration microsatellite mission, owned and operated by SSTL, to demonstrate low cost video-from-orbit space solution using COTS (Commercial-Off-The-Shelf) technologies . The 100 kg spacecraft flies a COTS telescope and HD (High Definition) video both of which have been adapted for the space environment and integrated into a custom-built framework. The imaging system is designed to deliver 1 m GSD (Ground Sample Distance) images and color HD video clips with a swath width of 5 km. 6) 7)
Carbonite 2 employs the SSTL-X50 platform, previously used on the experimental Carbonite-1 mission (launched in 2015 and operational in 2018). The SSTL-X50 satellite platform builds on three decades of experience at SSTL to realize a low-cost satellite bus for a wide range of missions, satisfying the lifetime requirements for Earth Observation and LEO communications operators. The baseline envelope for the SSTL-X50 platform is 65 x 65 x 72 cm; the microsatellites using the platform has a mass of about 100 kg at launch.
Figure 3: Carbonite-2 configuration (image credit: SSTL)
Figure 4: Illustration of the Carbonite-2 microsatellite (image credit: SSTL)
Several improvements have been introduced since basic video imaging capability was confirmed on Carbonite-1 (Ref. 14).
• Improved geolocation by the addition of a star camera
• Improved telescope and imager design
• Improved data capacity by a factor of x16 with two deployable solar arrays and greater memory capacity and data downlink
• Includes experimentation with additive design technologies, evolutionary design techniques and 3D printing.
The basic specifications for the Carbonite-2 spacecraft are provided in Table 1. The spacecraft configuration (Figure 3) illustrates that the imager is the dominant element, with avionics fitted around the imager.
Figure 5: Photo of the Carbonite Team with Carbonite-2 in the background (image credit: SSTL)
• November 2017: SSTL has shipped two small satellites, CARBONITE-2 and LEO Phase 1 (former LEO-1), to India in preparation for launch on ISRO's PSLV (Polar Satellite Launch Vehicle) from the Sriharikota launch site. 8)
• November 2017: British ‘New Space' pioneer Earth–i today announced that it has ordered the first five satellites from SSTL (Surrey Satellite Technology Ltd) for its new Earth Observation (EO) constellation. 9)
- The creation of Earth-i's constellation starts with the imminent launch of its preproduction prototype satellite which was also designed and manufactured in partnership with SSTL. This (Carbonite-2, alias VividX2) prototype will demonstrate and prove technology and processes for the future constellation including tasking, data downlinks to ground stations, image quality and video from space. The five SSTL satellites ordered today are planned to be launched in 2019.
Table 1: Carbonite-2 specifications
Launch: The Carbonite-2 pathfinder microsatellite (referred to as VividX2 in Earth-i terminology) was launched as a secondary payload on 12 January 2018 (03:59 UTC) on the PSLV-40 flight vehicle (XL configuration) of ISRO. The launch site was the SDSC (Satish Dhawan Space Center) SHAR (Sriharikota) on the east coast of India. The primary payload on this flight was CartoSat-2F (formerly CartoSat-2ER) of ISRO with a mass of 710 kg. 10) 11) 12)
Orbit: Sun-synchronous orbit with an altitude of 505 km and an inclination of 97.55º.
Figure 6: Illustration of the deployed Carbonite-2 microsatellite (image credit: Earth-i, SSTL)
The co-passenger satellites comprise one microsatellite and one nanosatellite from India as well as one minisatellite plus 2 microsatellites and 25 nanosatellites from six countries, namely, Canada, Finland, France, Republic of Korea, UK and USA. The total mass of all the 31 satellites carried onboard PSLV-C40 is about 1323 kg.
The 28 international customer satellites are being launched as part of the commercial arrangements between Antrix Corporation Limited (Antrix), a Government of India company under Department of Space (DOS), the commercial arm of ISRO and the International customers.
• TeleSat LEO Phase 1 (previously referred to as LEO-1), a communications minisatellite mission (168 kg) of Telesat Canada, built by SSTL, Surrey, UK.
• Carbonite-2, a microsatellite (~100 kg) of SSTL (X50 platform) to demonstrate video performance for the future Earth-i Vivid-i constellation. Earth-i is located at Surrey Research Park, Guildford, UK.
• IITMSAT [IIT (Indian Institute of Technology) Madras Satellite], also referred to as INS-1C (Indian Nanosatellite-1C), a student built microsatellite (11 kg) to study the energy spectrum of charged particles in the upper ionosphere.
• Microsat of ISRO in the 100 kg class, that derives its heritage from IMS-1 bus. This is a technology demonstrator and the forerunner for future satellites of this series. The satellite bus is modular in design and can be fabricated and tested independently of payload. 13)
• PicSat, a 3U CubeSat (3.5 kg) of the Paris Observatory, France. PicSat is an astronomy mission to measure exoplanetary transits.
• CANYVAL-X, 1, 2, a technology demonstration CubeSat mission (1U and 2U CubeSats) of Korea's Yonsei University and KARI (Korea Aerospace Research Institute) in collaboration with NASA; the goal is to demonstrate a Vision Alignment System.
• CNUSail-1 (Chungnam National University Sail-1), a 3U CubeSat solar sail test of Chungnam National University, Korea (4 kg).
• KAUSAT-5 (Korea Aviation University Satellite), a 3U CubeSat (4 kg) to observe the Earth with an IR camera and measure the amount of radiation around LEO.
• SIGMA (Scientific cubesat with Instruments for Global magnetic field and rAdiation) or KHUSAT-3 (Kyung Hee University Satellite-3), a 3U CubeSat to measure the global magnetic field and radiation.
• STEP CubeLab (Space Technology Experimental Project CubeSat Laboratory), a 1U CubeSat of Chosun University, Gwangju, Korea. The objective is to exploit core space technologies researched by domestic universities and verify the effectiveness of these technologies through on-orbit tests using the CubeSat.
• ICEYE-X1, Finland's SAR (Synthetic Aperture Radar) microsatellite with a mas of <100 kg.
• CICERO-7, a 6U CubeSat (~10 kg) of GeoOptics, USA, built by Tyvak, to demonstrate radio occultation observations.
• Arkyd-6A, a 6U CubeSat of Planetary Resources Inc., USA (formerly Arkyd Astronautics) to test attitude control, power, and communication systems as well as a photo-display-and-retransmission system.
• Fox-1D, a radio amateur and technology research 1U CubeSat, developed by AMSAT, USA and hosting several university developed payloads (University of Iowa, Virginia Tech, and Pennsylvania State-Erie).
• Lemur-2 x 4, 3U CubeSats of Spire Global Inc., San Francisco, CA.
• Landmapper-BC3 (Corvus-BC3), a 6U CubeSat (10 kg) of Astro Digital (former Aquila Space), USA to provide multispectral imagery of 22 m resolution on a swath of 220 km.
• MicroMAS-2a, a 3U CubeSat mission (3.8 kg) of MIT/LL (Massachusetts Institute of Technology/Lincoln Laboratory) of Lexington, MA, USA. Test of a compact microwave spectrometer and radiometer payload in orbit.
• SpaceBEE x 4 picosatellites, built to 0.25 CubeSat form factor, a technology demonstration, USA
• Flock-3p x 4, 3U CubeSats of Planet, San Francisco, USA.
• Tyvak 61C, a 3U CubeSat and a technology demonstration and astronomy mission of Tyvak Inc., Irvine CA, USA.
• October 2018: The Carbonite series of spacecraft are a series of demonstrators of new Earth Observation applications in preparation for commercial service missions. For some of these missions potential service providers and end-users work in partnership with SSTL (Ref. 6).
- Carbonite-2 results have already validated the approach to video imaging constellations and a range of applications, and paves the way for implementing full production spacecraft and constellations.
- Future iterations of the Carbonite-1 and -2 video imaging spacecraft are planned to be optimized for batch production to reduce mass and volume further, for implementation of a cost-effective constellation. Furthermore, the video imaging capability is also planned to be included as a separate capability onto the SSTL-300S1 and SSTL-1000S50 high resolution imaging spacecraft.
- In summary: Video imaging applications require constellations of very low cost, high-performance spacecraft. The highly bespoke design and production of satellites that has dominated the satellite industry would not be appropriate for such a constellation, and spacecraft addressing video imaging applications must be designed for batch production. The greatest risk for such batch production runs is the inadvertent introduction of systematic design faults and issues, and service demonstrators become essential in order to mitigate such risks.
- Carbonite-1 demonstrated that the concept of a COTS imaging payload is viable, and led to a range of lessons learned that were then implemented on a second Carbonite-2 pilot service demonstrator mission.
- Carbonite-2 has returned high quality results which can give owner operators confidence that high resolution video imaging constellations can be implemented at a low cost in order to address emerging markets.
• August 2018: Carbonite-1 is still operational after two years, and is sharing its groundstation passes with other commercial satellites operated by SSTL. The satellite is still being used to test out new improved AOCS and imaging techniques and to build heritage on the payload equipment. 14)
- The Carbonite-1 and -2 microsatellites launched in 2015 and 2018, respectively, are delivering high-resolution, high-definition color video from space, providing a new dimension to Earth Observation and "big data" analytics. Single video imaging spacecraft have limited utility. In order to fully benefit from such spacecraft requires cost-effective observations with multiple opportunities per target per day, driving the need for large-scale constellations of ultra-low cost spacecraft. The first constellation based on the two pilot missions is now in production, and will start commercial operation by 2020. Still-imagery has a number of limitations in applications related to surveillance, disaster monitoring and news gathering. Video can provide additional contextual information, and space borne video systems have been demonstrated several times over the past decades. Single video imaging spacecraft in LEO are limited in application, as they cannot cover specific target areas on the globe frequently enough. Furthermore, previous video imaging missions have generally lacked the necessary resolution to allow fine scale human activity to be monitored, such as traffic and crowds.
- The spacecraft will now be used to demonstrate real operational scenarios with data being shared with key mission partners. Over 450 videos were captured in the first 100 days of operations, with data being shared with key mission partners.
• July 18, 2018: Today marks Nelson Mandela's 100th birthday, with the 18th of July officially declared internationally as Mandela Day by the United Nations in 2009. Each year the day honors the former president of South Africa as he fought tirelessly for human rights and championed freedom, both in South Africa and globally. 15)
Figure 7: On 4 April 2018, the Carbonite-2 VividX2 satellite captured full-color video footage of a large mural celebrating the life of Nelson Mandela, created by 106 men at Zonderwater Correctional Center. The impressive mural, made from many individual blankets stitched together, is clearly visible from space. The project was initiated by 67 Blankets, a campaign which works in unison with Nelson Mandela Day to introduce crocheting into the curriculum of correctional services (image credit: Earth-1)
• July 17, 2018: Earth-i today announced that a consortium it is leading has received a grant from the Centre for Earth Observation Instrumentation (CEOI), funded by the UK Space Agency. 16)
- The project will be used to develop a number of new Earth Observation technologies that will enable processes, such as the enhancement of image resolution, cloud-detection, change detection and video compression, to take place on-board a small satellite rather than on the ground. This will accelerate the delivery of high-quality images, video and information rich analytics to end-users.
- On-board cloud detection will make the tasking of satellites more efficient and increase the probability of capturing a usable and useful image or video. To achieve these goals, ‘Project OVERPaSS' will implement, test and demonstrate very high-resolution optical image analysis techniques, involving both new software and dedicated hardware installed onboard small satellites to radically increase their ability to process data in space.
- The project will also determine the extent to which these capabilities could be routinely deployed on-board British optical imaging satellites in future.
- Earth-i's Vivid-i constellation offers a potential first application for the OVERPaSS technology, enabling a wide range of clients in industry and government to benefit from the higher quality imagery, video and analytics, and faster processing and delivery times, that OVERPaSS could enable.
- Earth-i's partners in the consortium are:
a) Cortexica Vision Systems, a leading provider of cloud-based image and video recognition systems
b) University College London (UCL), through the UCL Mullard Space Science Laboratory (UCL MSSL) with its extensive experience in space research missions
c) Surrey Satellite Technology Ltd. (SSTL), a world leader in the design, manufacture and launch of small satellites and unique in that it designs and manufactures a significant proportion of its satellite payloads, subsystems and equipment in-house.
- Chief Technology Officer for Earth-i, John Linwood said: "This is another example of how the UK Space industry continues to invest collectively in new technologies and innovation. Our goal with OVERPaSS is to develop further world-beating capabilities to ensure that British satellites remain at the forefront of the global space industry for the benefit of customers worldwide."
- Launched on12 January 2018, VividX2 is the world's first commercial satellite able to provide full-color video of life on Earth. With a mass of 100 kg. and measuring approximately 1 cubic meter, VividX2 is orbiting at 505 km. above the Earth and traveling at approximately 7 km/s. At the heart of the satellite is an Ultra High Definition (UHD) camera that captures high-resolution images for any location on Earth — and also films up to two minutes of video at a time as the satellite passes over each target location.
- The newly released video footage was taken as VividX2 passed over a range of targeted locations under the craft's sun-synchronous polar orbit. The clips show videos of numerous different locations across the globe, and some of the intriguing new insights that can be quickly derived from the video. These first sequences represent just a fraction of the data already collected by VividX2 and demonstrate Earth-i's ability to deliver an unprecedented level of detail in FMV (Full Motion Video), while also extracting still imagery to meet an ever-wider range of needs.
- The new videos and still images can be found at: http://earthi.space/colourvideofromspace
Figure 8: Screenshot captured from the Carbonite-2 satellite video imaging the Dubai Airport (image credit: SSTL)
- Earth-i is showcasing the first color videos from VividX2, and demonstrating potential applications, at the 34th Space Symposium in Colorado Springs on 16-19 April, and at the GEOINT geospatial intelligence exhibition in Tampa on 23-25 April. Visitors to these major industry events will be able to discuss Earth-i's range of innovative new capabilities including:
1) The provision of high definition images and color video with resolutions better than one meter for any location on Earth
2) The ability to capture and analyze moving objects such as vehicles, vessels and aircraft in Ultra High Definition color video
3) Revisiting the same location multiple times per day with agile satellites that can be pointed to image specific areas of interest and acquire high-frame rate imagery
4) Rapid tasking of satellites to take images or video, and fast data download within minutes of acquisition
5) Delivering additional contextual depth of information from motion and time — the 4th dimension
6) The current VividX2 mission is the product of a unique collaboration between Earth-i, the Ministry of Defence, Defence Science and Technology Laboratories (DSTL) and Surrey Satellite Technology Ltd (SSTL), all of the UK Richard Blain, CEO of Earth-i, said that commercial color video from space represents a major breakthrough for the industry and a world first. This initial footage shows what is now possible — with more videos being acquired every day. The depth and quality of data the company can now acquire takes Earth Observation (EO)-based big data analytics to a new level. The way Earth-i captures video allows for a broader range of contextual insights to be derived than is possible with traditional still imagery.
- Richard Blain, CEO of Earth-i, said that commercial color video from space represents a major breakthrough for the industry and a world first. This initial footage shows what is now possible — with more videos being acquired every day. The depth and quality of data Earth-i can now acquire takes Earth Observation (EO)-based big data analytics to a new level. The way video is captured allows for a broader range of contextual insights to be derived than is possible with traditional still imagery.
- He added that processing techniques, such as image stacking, can be applied to high frame rate video to increase effective resolution to levels as good as 60 cm. for still and video imagery. With the rich data being received from VividX2, the company is improving and developing advanced data analytics, new capabilities and insights from intelligent platforms, including the use of computer vision and machine learning.
- Graham Turnock, Chief Executive of the UK Space Agency, added that the UK has a long history of innovation and is now demonstrating the world's first commercial satellite that can capture full color video of Earth from space. With applications ranging from defense to disaster response, this is a great example of the strength of the UK space sector, which the agency continues to support as part of the Government's Industrial Strategy.
- Sarah Parker, the Managing Director of SSTL, noted that successful acquisition of the satellite's first color video from space is a pivotal moment in the development and deployment of this new technology — work has already begun on the manufacture of the next batch of five production satellites for Earth-i's Vivid-i constellation while they develop new applications from a stream of video data from VividX2.
- Earth-i is also investing heavily in its big data analytics systems to enable easy acquisition and analysis of imagery, and the use of advanced algorithms and machine learning to extract further value from the unique data gathered by its constellation.
• January 12, 2018: SSTL has confirmed the successful launch of CARBONITE-2, an Earth Observation technology demonstration mission owned and operated by SSTL, and of the Telesat LEO Phase 1 communications satellite, an important milestone in Telesat's plans to deploy a global low earth orbit (LEO) constellation that will revolutionize broadband communications services around the world. 20)
- Following separation from the launch vehicle, SSTL is pleased to confirm that successful contact was made with both satellites and all initial system checks for both spacecraft are nominal.
- SSTL's spacecraft operators will complete commissioning and orbit-raising maneuvers for the satellite from SSTL's Spacecraft Operations Centre in Guildford. Once the Telesat LEO Phase 1 satellite has reached its final planned orbit, command will be handed over to Telesat for in-orbit operation using the Ka-band payload from Telesat's ground station at Allan Park in Canada.
• Cartosat-2F and 29 of the PSLV's secondary payloads separated from the PSLV in a 505 km sun-synchronous type orbit in the first 25 minutes of the mission. All satellites separated in 7 minutes (Ref. 10).
- The fourth stage of PSLV-C40 fired twice for short durations to achieve a polar orbit of 365 km height in which India's Microsat successfully separated.
Sensor complement of Carbonite-2 (UHD)
At the heart of the new satellite is an UHD (Ultra High Definition) camera which will capture high-resolution images for any location on Earth – and film up to two minutes at a time of video which can show moving objects such as vehicles, vessels and aircraft. The camera is a 4k UHD video instrument. Currently, the satellite can record only 2 minutes of 4k video at a time, but this is after all only a viability test operation aimed at showing that the dedicated 4k video recording platform functions smoothly.
Note: More detail of the Carbonite-2 spacecraft and the sensor complement will be provided when the information becomes available.
Table 2: Carbonite-2 specifications
With the enhanced AOCS, several imaging modes are supported in snapshot and video mode. These include Stripmap, Stereo pair, and mosaic imaging. In video mode target tracking mode is also supported.
In strip mapping mode, video imaging results in a number of overlapping scenes providing opportunities to address applications for low light or high quality imaging through image processing of the combined overlapping scenes.
The instrument includes a focusing mechanism, and payload commissioning in video imaging mode while moving the focusing mechanism allows very rapid instrument focusing to be achieved.
Figure 9: Carbonite-2 imaging modes (image credit: SSTL)
Ground Segment and image processing
The applications of high resolution video from space are numerous, as this class of data provides the necessary spatial and temporal resolution to monitor human activity and pattern-of-life. Conventional wisdom would suggest that small satellites are not well suited to this mission profile: the laws of diffraction dictate that to obtain a higher spatial resolution, a larger aperture is required, whereas small satellites are by definition limited in volume. This problem is exacerbated by video, where exposure time and therefore the signal-to-noise ratio of the resultant video are highly constrained. The Carbonite-2 mission reconciles these challenges by leveraging principles of computational photography and the latent richness in the data collected. The video collected by Carbonite-2 is enhanced in software through ground processing, through corrections derived from ground and on-orbit characterization, as well as by exploiting the high redundancy in this video data and the contextual information inherent in its high resolution. In-orbit results demonstrated that this approach can result in a spacecraft that can address a range of novel video imaging applications so far hardly explored and exploited in previous Earth Observation Missions (Ref. 6).
The block diagram for the image processing chain for Carbonite-2 is shown in Figure 10. The image processing chain corrects for the measured radiometric performance of the sensor, and supports both strip mapping as well as video imaging. - The ground processing also exploits the high redundancy inherent in the resulting video data, and the contextual information inherent in its high resolution.
Figure 10: Carbonite-2 processing chain (image credit: SSTL)
The standard COTS instrument is responsive to NIR (Near-Infrared), which is undesirable when it is necessary to represent realistic image reproduction for applications such as news casting and media. A NIR filter was applied to change the imager spectral response on Carbonite-2.
On the ground, fixed pattern noise, dark current and noise, and read noise were measured by capturing images with the camera's lens cap on, such that the sensor was shielded from light. A raw image that represents this is shown in Figure 11.
Figure 11: Sensor Fixed Pattern Noise (image credit: SSTL)
The fixed pattern noise (FPN), which represents how the bias of the sensor changes from pixel to pixel, was measured on-ground by capturing and averaging a series of 50 dark images, each containing 10 µs exposure time. This was the minimum configurable exposure time, and serves to minimize the effects of dark current. Further exposures of 7 seconds also help characterize the effect of exposure time, so that ultimately images can be corrected accordingly.
Sensor Read Noise was characterized by subtracting the FPN from the minimum exposure dark images, resulting in a standard deviation of 2.48 ADU (Analog-to-Digital conversion Unit), which was assumed to be equivalent to the read noise and closely matches datasheet specifications.
Dark Current was measured by placing the image sensor in a temperature controlled chamber and capturing dark images at different stable temperatures, and at different exposure times. Only one dark image was captured at each of these exposure times, along with a bias frame was using the minimum possible exposure time (10 µs), such that each dark image could be bias corrected. Measurements showed that there is negligible dark current across the operational temperature and exposure ranges which also matches datasheet specifications.
The sensor's datasheet has indicated that its dynamic response is linear, except very near to saturation. This was also qualitatively verified by capturing images from an integrating sphere with many different exposure times, and examining the response of a single pixel (the radiance of which is constant across images). As a result the dynamic range was established to be 52.3dB, which is 4dB worse than the typical value stipulated on the sensor datasheet.
The photo-response non-uniformity (PRNU) represents how the gain of the image sensor changes from pixel to pixel. This was measured by imaging an integrating sphere with a transmissive diffuser over the output port. Likewise, the image sensor was brought as close to the integrating sphere as possible, such that its housing was touching the diffuser, to ensure a flat field of radiance at the sensor. Images were also captured with the image sensor at different angles and averaged to mitigate any systematic effects induced by the apparatus. Thus, the averaged image has been assumed to roughly represent the PRNU.
The signal to noise ratio of the image sensor was verified by scanning an 8 x 8 pixel window across the images captured from the integrating sphere as described for the PRNU determination, for each color channel separately. No attempt was made to correct images for FPN or PRNU due to the artefacts contained in each, and the use of a small window size should alleviate the need to do so. The radiance was assumed to be a flat field across this window. The signal-to-noise ratio was then determined by taking the ratio of the mean signal and the standard deviation of the signal in this window (both in ADU).
The resulting SNR plots confirm datasheet figures and can be used to evaluate the in-orbit performance of the imager that is achieved. In-orbit results show good agreement with radiometric models used during the instrument design.
Carbonite-2 In-Orbit Results
Carbonite-2 was launched on 12 January 2018. As part of the commissioning campaign, the spacecraft was contacted from the SSTL groundstation in Surrey on the first pass to start platform checkout and detumble the spacecraft and bring it under 3-axis control.
The UHD instrument includes a focusing mechanism, and payload commissioning in video imaging mode while moving the focusing mechanism allows very rapid instrument focusing to be achieved.
In order to find the best focus in-orbit, a coarse focus sweep was performed whilst imaging on two different acquisitions over Doha and Mumbai. The direction of the sweep was opposite in order to reduce uncertainty with residual backlash. A total focus range of ± 940 µm was covered during the sweep of 200,000 steps in the range. As the payload is changing focus whilst imaging, the image quality changes from blurred to sharp to blurred again and the point where it is the sharpest is called 'best focus'. To find this optimal position, a proprietary algorithm to quantify sharpness was used on each of the frames obtained during the acquisition. The frames have minimal change over time given the Forward Motion Compensation (FMC) maneuver during imaging. The image of Figure 12 illustrates the process:
Figure 12: On-orbit focusing (image credit: SSTL)
The results of the focusing match between the two images. Furthermore estimates of the BTF at the best focus point indicate that the same performance is achieved as measured prior to launch.
Following commissioning, the spacecraft was used to demonstrate real operational scenarios with data being shared with key mission partners . 21) Over 450 videos were captured in the first 100 days of operations, with data being shared with key mission partners (see Figure 8).
Not everything has gone to plan, and problems with the on-board image sensor module operation have prevented the mission from being able to support extended pilot services as planned. A similar imager unit has been in use successfully used on Carbonite-1 for over three years to date. Although fixing this issue on future production models is relatively straightforward, it highlights the importance of technology testing and demonstration in a fully representative manner, and also validates the decision of going ahead with Carbonite-2 as a second risk reduction mission.
Vivid-i Commercial Microsatellite Constellation — Pathfinder Carbonite-2 / VividX2
The British company Earth-i of Surrey Research Park, Guildford, UK. specializes in the acquisition, processing and delivery of image data from Earth Observation satellites, in particular the DMC3/TripleSat Constellation and the KOMPSAT series of optical and radar satellites.
Im May 2017, Earth-i announced plans to launch and operate Europe's first commercial constellation offering both video and imagery – and the first in the world to provide full-color video footage. — Earth-i is headquartered in Guildford in the Surrey Research Park near a number of other UK space-related companies including SSTL – as well as SSC (Surrey Space Center) at the University of Surrey. 22)
The launch of its own constellation is a natural evolution of Earth-i's existing and well-regarded image and Earth Observation analytics business. The constellation will enable Earth-i to meet rapidly growing demand for high-resolution EO (Earth Observation) data, and big data analytics and insights drawn from this data.
Traditionally, extracting value from Earth Observation data has been the preserve of Governments and some larger corporations. Earth-i is now at the forefront of an era known as New Space. This is being driven by commercial organizations that want to improve investment and trading decisions, monitor and track their assets more cost-effectively, track change or activity in critical locations – and predict future events with more certainty.
In January 2018, SSTL and Earth-i announced the launch Carbonite-2, a technology demonstration microsatellite mission developed, operated and owned by SSTL (Surrey Satellite Technology Ltd .); this mission is referred to as VividX2 by the Earth-i team. The objective is to demonstrate and prove technology and processes for Earth-i's forthcoming Vivid-i constellation including tasking, data downlinks to ground stations, image quality and the complex motion control systems that enable the spacecraft to capture video from space. 23)
Earth-i is at the forefront of an era known as New Space which is being driven by commercial and governmental organizations that want to use high-quality, timely images and video from space to improve investment and trading decisions, monitor and track their assets more cost effectively, track changes or activities in critical locations – and predict future events with more certainty.
Earth-i is working with the space industry's most innovative and dynamic companies. Earth-i has already ordered the next five satellites for its Vivid-i constellation from SSTL; appointed Norway's KSAT (Kongsberg Satellite Services) to provide ground network services; and commissioned software from Swedish photogrammetry and imagery specialist, Spacemetric, to manage, catalog and geometrically correct images and video from its new prototype satellite.
Josef Aschbacher, Director of Earth Observation Programs at ESA (European Space Agency ) said that the launch of VividX2 is a significant next development of Earth-i's constellation, and welcomed by ESA. The Vivid-i Constellation will provide capabilities they haven't seen before including full-color video, and an assured stream of high-quality data from space to help improve both the planet and lives on Earth.
Earth-i's Vivid-i Constellation will be a major leap forward for the Earth Observation industry providing a number of innovative capabilities including:
• The provision of high-frame rate images with resolutions better than one meter for any location on Earth.
• The ability to film moving objects such as vehicles, vessels and aircraft in Ultra High Definition color video.
• Revisiting the same location multiple times per day with agile satellites that can be pointed to image specific areas of interest.
• Rapid tasking of satellites to take images or video, and fast data download within minutes of acquisition.
Richard Blain, CEO of Earth-i, said that the launch of VividX2 (Carbonite-2) on 12 January 2018 is a significant milestone for Earth-i and for the global space industry. It's the culmination of much hard work by the teams at Earth-i and SSTL. They are now researching and testing the technology and data services for the Vivid-i Constellation using the still and video imagery from this prototype – and showing their customers what will be possible in the future from new capabilities such as color video from space.
The planned Vivid-i constellation will consists of 15 microsatellites, launched into a sun-synchronous orbit of 500 km. The Vivid-i constellation will provide imagery with the following characteristics:
• Resolution: 60 cm (super resolution), 1 m GSD & full motion, full color video
• Image size: 5.2 km x 5.2 km, fixed frame geometry
• Bands: 3 band true color, Bayer filter
• Revisit: Minimum 2 revisits per day globally; additional revisits as the constellation builds.
Richard Blain explained: "As for the Vivid-i constellation, we will launch that in batches of five. And in terms of the architecture, our baseline plan is for the first batch to go into one orbital plane, and then for the following batches to go into different planes, so that not only do we get high-frequency revisit to places on Earth, but we also get to see places at different times of the day."
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2) Nimal Navarathinam, Andrew Cawthorne, Luis Gomes, Martin Sweeting, John Paffet, "DMC3 and Carbonite-1: Two Sides of Small Satellites," Proceedings of the 30th Annual AIAA/USU SmallSat Conference, Logan UT, USA, August 6-11, 2016, paper: SSC16-III-10, URL: https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=3354&context=smallsat
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6) Juan Fernandez-Saldivar, Alex da Silva Curiel, Steve Knox, John Gilby , Andrew Cawthorne, Luis Gomes, Sir Martin Sweeting, "On-orbit video from Carbonite-2: Towards software-defined Earth observation," Proceedings of the 69th IAC (International Astronautical Congress) Bremen, Germany, 1-5 October 2018, paper: IAC-18-B4.4.3, URL: https://iafastro.directory/iac/proceedings/IAC-18/
7) Jonathan Amos, "UK satellite to make movies from space," BBC News, 12 Jan. 2018, URL: http://www.bbc.com/news/science-environment-42654281
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9) "Earth-i Orders Satellites from SSTL for World's First Full-Color Video Constellation," Earth-i Press Release, 21 Nov. 2017, URL: http://earthi.space/press/earth-i-orders-satellites-worlds-first-full-colour-video-constellation/
10) "PSLV Successfully Launches 31 Satellites in a Single Flight," ISRO, 12 Jan. 2018, URL: https://www.isro.gov.in/update/12-jan-2018/pslv-successfully-launches-31-satellites-single-flight
11) Stephen Clark, "India's PSLV lifts off on first flight since fairing failure," Spaceflight Now, 12 January 2018, URL: https://spaceflightnow.com/2018/01/12/pslv-c-40-coverage/
12) "Earth-i launches prototype of world's first full-color, full-motion video satellite constellation," Space Daily, 16 Jan. 2018, URL: http://www.spacedaily.com/reports/Earth_i_launches_prototype_of_worlds_
14) Alex da Silva Curiel, Andrew Haslehurst, Kieran O'Brien, Nimal Navarathinam, Simon Prasad, Chris Saunders, Rachel Bird, Liam Sills, Andrew Cawthorne, Luis Gomes, Martin Sweeting, "Watching the world go by," Proceedings of the 32nd Annual AIAA/USU Conference on Small Satellites, Logan UT, USA, Aug. 4-9, 2018, paper: SSC18-II-08, URL: https://digitalcommons.usu.edu/cgi/viewcontent.
15) "VividX2 Captures Mural for Nelson Mandela Day 2018," Earth-i, 18 July 2018, URL: http://earthi.space/blog/vividx2-captures-nelson-mandela-mural/
16) "Earth-i leads consortium to develop on-board processing for video imagery from space," Earth-1, 17 July 2018, URL: http://earthi.space/press/consortium-secures-grant/
18) "Earth-i releases its first full-colour video of Earth taken from space," Earth-i, 16 April 2018, URL: http://earthi.space/press/earth-i-releases-first-full-colour-video-earth-taken-space/
19) "SSTL releases first full colour videos from CARBONITE-2," SSTL, Press Release, 16 April 2018, URL: https://www.sstl.co.uk/media-hub/latest-news/2018/
20) "SSTL confirms the successful launch of CARBONITE-2 and Telesat LEO Phase 1 satellite," SSTL News & Events, 12 Jan. 2018, URL: https://www.sstl.co.uk/Press/SSTL-confirms-
21) "UK Eyes Rapid Military Smallsat Deployment," Aviationweek, 18 April 2018, URL: http://aviationweek.com/space-symposium/uk-eyes-rapid-military-smallsat-deployment
22) "Earth-i Announces Plans For Europe's First Commercial Video Satellite Constellation," Earth-1, 30 May 2017, URL: http://earthi.space/press/earth-i-announces
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (firstname.lastname@example.org).