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ALOS-3

The Advanced Land Observing Satellite-3 (ALOS-3), also known as Daichi-3, was an optical Earth observation satellite developed by the Japan Aerospace Exploration Agency (JAXA) as the successor to the optical observation mission of the original ALOS (Daichi). Designed to deliver high-resolution panchromatic imagery at 0.8 m resolution across a 70 km swath width, along with multispectral bands at 3.2 m resolution, ALOS-3 aimed to support disaster management, environmental monitoring, cartography, infrastructure surveillance, and resource surveying by providing wide-area, precise optical data. Launched on March 7, 2023, from Tanegashima Space Center aboard the inaugural H3 rocket, the mission failed shortly after liftoff when the second-stage engine malfunctioned and failed to ignite, leading to a destruct command and the loss of the satellite before it could reach orbit. ALOS-3's primary objectives centered on enhancing Japan's capabilities for rapid and global geospatial information infrastructure, including urgent observations of earthquakes, floods, and wildfires, as well as ongoing monitoring of , vegetation changes, and urban development. The incorporated the Advanced Optical Sensor (AOS), a sophisticated system with six multispectral bands ranging from 0.40 to 0.89 μm, enabling detailed analysis for both and applications. Its planned at 669 km altitude and 10:30 a.m. local at the descending node would have facilitated a 35-day revisit cycle, with sub-cycles as short as three days for targeted areas. Weighing approximately 3 metric tons and measuring 5.0 m in height, 16.5 m in length (with solar arrays deployed), and 3.6 m in width, ALOS-3 was engineered for a seven-year operational lifespan and featured multiple imaging modes such as strip map for standard wide-area coverage, stereoscopic for mapping, pointing for off-nadir targeting up to 60 degrees, and mosaic for large-scale seamless imagery. These capabilities represented a significant upgrade over predecessors, balancing high resolution with broad coverage to meet diverse user needs, including contributions to international frameworks like the (). Despite the launch failure, the ALOS follow-on program continued with complementary missions, such as the radar-focused ALOS-4. Following the failure, is discussing a follow-on advanced optical , potentially launching around 2028.

Background

Development history

The Advanced Land Observing Satellite-3 (ALOS-3), also known as Daichi-3, emerged from JAXA's efforts to continue the ALOS series after the original ALOS-1 mission ended in , with conceptual planning for follow-on optical capabilities beginning in the late . By , initial designs for an advanced optical were presented, emphasizing high-resolution imaging to support national needs in mapping and monitoring. The project gained formal momentum in the early as part of JAXA's broader program, approved within Japan's space initiatives to address gaps left by ALOS-1's optical focus and ALOS-2's shift to in 2014. Development of ALOS-3 was contracted to Electric Corporation, which utilized an adapted from ALOS-2 to streamline construction and reduce costs, with primary work starting around 2015 under oversight. This timeline aligned with initial launch projections for 2015 or later, though delays pushed the attempt to 2023 due to integration challenges and evolving priorities in Japan's space sector. The project bridged the optical observation capabilities of ALOS-1—particularly improving upon its sensor's resolution and swath limitations—while complementing ALOS-2's emphasis to provide comprehensive data coverage. Budget allocations supported these efforts, totaling approximately 38 billion yen for development, with annual increments such as 8.9 billion yen in 2019 and 14.9 billion yen in 2020, including supplementary resources. ALOS-3's evolution integrated closely with 's national space strategy, particularly the Basic Space Law and subsequent policies emphasizing disaster management, environmental monitoring, and geospatial infrastructure development. As a key asset for rapid response to natural calamities like earthquakes and tsunamis—drawing from lessons of the 2011 Great East Japan Earthquake—the satellite was positioned to deliver timely high-resolution imagery to central and local governments, enhancing national resilience and international cooperation in . Key milestones included sensor prototyping and validation in the late , culminating in system-level testing to ensure compatibility with JAXA's operational framework before launch preparations.

Mission objectives

The primary mission objectives of ALOS-3 centered on enhancing societal safety and security through advanced capabilities, particularly in management and the provision of timely geospatial for governmental responses. Specifically, the satellite was designed to support rapid mapping and monitoring of such as earthquakes, floods, and wildfires, enabling urgent pre- and post-event imagery to aid in damage assessment and recovery efforts for central and local governments in and beyond. This focus addressed the need for high-resolution, wide-area imaging to contribute to a safer society by facilitating quick decision-making in crisis situations. A key goal was the creation and continuous updating of fundamental geographic information, including topographic maps, land use patterns, and digital elevation models, to serve as a foundational resource for national and development. ALOS-3 aimed to enable resource for applications in , , and energy sectors, such as assessing yields, health, and potential sites for , gas, or . Additionally, it targeted , with emphasis on coastal zones for and sea-level changes, as well as vegetation health to track , , and dynamics. To achieve these objectives, ALOS-3 was engineered for integration with the broader ALOS series, particularly complementing the radar-based observations of ALOS-2 to provide all-weather, day-night optical data synergy for comprehensive environmental and disaster analysis. Performance targets included achieving a ground of 0.8 meters over a 70 km swath width, allowing for efficient nationwide coverage of —approximately every 1.5 months—and contributions to global datasets for international collaboration on geospatial research and monitoring. These capabilities represented a significant advancement over its predecessor, ALOS-1, by improving the threefold to 0.8 m while maintaining the 70 km observation swath for practical applications.

Spacecraft design

Specifications

The ALOS-3 spacecraft, also known as Daichi-3, features physical dimensions optimized for launch and deployment in orbit. It measures 5.0 m in height, 16.5 m in span with the solar panels fully deployed, and 3.6 m in width, with a launch mass of approximately 2,900 kg. These parameters enable efficient accommodation on the H3 launch vehicle while supporting the deployment of its optical imaging payload. The is designed for a nominal mission lifetime of 7 years, ensuring long-term capabilities for applications such as disaster monitoring and land management. Its power subsystem relies on deployable solar arrays that generate up to 5.3 kW of electrical power at the end of life, complemented by batteries for eclipse operations. control mechanisms are incorporated to maintain structural and optical , minimizing distortions from orbital variations to preserve . ALOS-3 operates in a sun-synchronous at an altitude of 669 km, with a local of 10:30 a.m. (±15 minutes) at the descending node. This configuration provides a 35-day repeat cycle, augmented by a sub-cycle of approximately 3 days that facilitates agile pointing for frequent revisits to areas of interest. The orbit inclination and timing optimize illumination conditions for high-resolution optical observations across diverse latitudes.

Key subsystems

The attitude and orbit control subsystem of ALOS-3 enables high-precision pointing and agile maneuvering essential for wide-area observations and . It incorporates body-pointing capabilities of up to ±60 degrees off- in any direction, allowing the satellite to observe areas beyond its nadir track efficiently. These components facilitate precise geolocation of images and contribute to the satellite's ability to perform rapid off-nadir acquisitions. The propulsion subsystem supports maintenance of the at approximately 669 km altitude and initial post-launch adjustments. The onboard computer subsystem handles command execution, management, and fault protection, enhancing overall system reliability in the harsh space environment.

Instruments and sensors

Optical payload

The primary instrument of ALOS-3 is the Wide-swath and high-resolution optical Imager (WISH), serving as the successor to the Panchromatic Remote-sensing Instrument for Stereo Mapping () on ALOS-1. WISH employs an off-axis four-mirror optical system to achieve high-resolution imaging over a broad area, enabling simultaneous capture of detailed panchromatic and multispectral data. The panchromatic band operates in the spectral range of 0.52–0.76 μm, providing a ground of 0.8 m and a swath width of 70 km at . This configuration supports high-fidelity black-and-white imagery suitable for applications requiring precise structural details, such as and . Complementing the panchromatic capability, WISH includes six multispectral bands with a ground of 3.2 m and the same 70 km swath width. These bands cover 0.40–0.45 μm (coastal blue), 0.45–0.50 μm (blue), 0.52–0.60 μm (green), 0.61–0.69 μm (red), 0.69–0.74 μm (), and 0.76–0.89 μm (near-infrared), expanding from the four bands of ALOS-1's Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) to enhance vegetation analysis, assessment, and classification. Key enhancements in WISH over ALOS-1 instruments include a larger optical and upgraded detectors, allowing for the 0.8 m and 70 km swath without the stereo trade-offs of , while achieving radiometric accuracy of ±5% relative and ±10% absolute for multispectral bands. These improvements enable more efficient wide-area coverage with higher detail, supporting advanced needs.

Data handling and transmission

The data handling system of ALOS-3 incorporates solid-state recorders designed to buffer high-volume observations during periods without direct ground contact. This capacity supports the mission's daily data generation, which can exceed 1 TB, by accommodating uncompressed and compressed datasets from the optical sensors prior to downlink. Onboard processing includes real-time compression using JPEG2000 or equivalent algorithms, achieving a data volume reduction of approximately 4:1 for panchromatic imagery while preserving essential image quality. This compression, applied immediately after sensor capture, also embeds metadata such as geolocation tags, timestamps, and attitude information derived from the spacecraft's navigation systems, facilitating precise post-mission analysis without additional onboard computation overhead. Data transmission relies primarily on a high-speed Ka-band link operating at 1.8 Gbps for direct downlink of compressed imagery to ground stations, optimized for large-volume transfers during overpasses. A backup X-band channel at 0.8 Gbps provides redundancy for critical data in case of Ka-band anomalies. Additionally, an optical laser communication system at 1.8 Gbps enables inter-satellite links, allowing data relay to other assets in orbit for enhanced flexibility in global coverage.

Launch

Launch vehicle and preparation

The ALOS-3 mission utilized the H3-22S configuration of the launch vehicle, marking the inaugural flight of this new flagship rocket jointly developed by the Japan Aerospace Exploration Agency () and (MHI). The series is designed as a successor to the and rockets, emphasizing cost-effectiveness, flexibility, and high reliability through innovations like the engines powering the second stage, which employ an expander bleed cycle for improved efficiency. This configuration, with two solid rocket boosters, was selected to deliver the approximately 3-ton ALOS-3 satellite to its planned , ensuring compatibility with the spacecraft's mass and dimensional requirements. The launch site was Yoshinobu Launch Pad 2 (LP2) at the in , , a facility optimized for medium- to heavy-lift vehicles and equipped for handling liquid-propellant rockets like the H3. This pad supports vertical integration of the rocket stages and payload, facilitating efficient assembly in a controlled environment to mitigate risks associated with the debut flight. Pre-launch preparations commenced with the shipment of the ALOS-3 satellite to Tanegashima in late 2021, followed by integration with the H3 rocket in 2022 to verify interfaces, electrical connections, and structural compatibility. Subsequent activities included propellant loading simulations, system checks for the LE-9 engines and solid boosters, and multiple countdown rehearsals to ensure synchronization between ground support equipment and the vehicle's flight termination systems, given the high-stakes nature of the inaugural mission. An initial launch attempt on February 17, 2023, at 01:37 UTC was aborted moments after main engine start when the solid rocket boosters failed to ignite properly, leading to a safe shutdown without liftoff. As the primary payload, ALOS-3 underwent environmental testing at the site prior to encapsulation in the fairing, with the overall effort coordinated under JAXA's Test Flight No. 1 (H3 TF1) designation to validate the rocket's performance baseline.

Mission timeline and failure

The H3 launch vehicle carrying ALOS-3 lifted off from on March 7, 2023, at 01:37:55 UTC (10:37:55 JST). The first stage, powered by two engines, performed nominally, achieving separation at approximately T+5 minutes. Telemetry indicated normal operations up to the first stage shutdown at T+4 minutes 56 seconds. The second stage ignition sequence began at T+5 minutes 16 seconds but failed due to an event in the stage's propulsion system controllers, preventing the LE-5B-3 engine from firing. This halted the ascent, rendering orbital insertion impossible. ground control activated the flight termination system (FTS) at 01:51:50 UTC (10:51:50 JST), approximately T+13 minutes 55 seconds after liftoff, destroying the vehicle to ensure public safety. The resulting debris, including the ALOS-3 satellite, fell into the east of the on the same day, with no reported risks to crew, aircraft, or ground populations. Following the failure, JAXA established a special investigation board, which concluded in October 2023 that the root cause was an in the second-stage , stemming from a design vulnerability in power distribution. Three potential failure scenarios were identified, leading to implemented across the H3 program to enhance reliability. The incident resulted in the total loss of the ALOS-3 mission, delaying subsequent H3 launches until February 2024, while JAXA archived ground test data from the vehicle's subsystems for future analysis.

Planned observation modes

Strip map observation mode

The strip map observation mode serves as the default imaging configuration for ALOS-3, enabling continuous along-track scanning to acquire linear image strips of the Earth's surface. This mode facilitates routine high-resolution mapping by capturing data in a swath width of 70 km, extending up to 4,000 km in length per orbital pass, which supports extensive coverage without the need for complex maneuvering. In this nadir-pointed mode, ALOS-3 simultaneously acquires panchromatic imagery at 0.8 m and multispectral imagery at 3.2 m using its advanced optical , allowing for detailed representations suitable for various analytical purposes. The prioritizes in data collection, with the satellite's designed to revisit areas regularly, achieving complete coverage of Japan's land areas within its 3-day sub-cycle period. As the baseline observation approach, strip map mode is primarily applied to for updating topographic maps at scales like 1:25,000 and to resource surveys for monitoring , , and coastal environments. It provides foundational data for disaster management and , offering consistent high-fidelity strips that form the core of ALOS-3's operational dataset.

Stereoscopic observation mode

The stereoscopic observation mode of ALOS-3 facilitates the creation of stereo pairs by acquiring images from forward and backward viewing angles during a single orbital pass, with off-nadir angles up to 30 degrees to optimize the base-to-height (B/H) ratio for enhanced accuracy. This mode, designated as 3D1, targets specific scenes by leveraging the satellite's agility from reaction wheels to adjust pointing directions, though it may yield a suboptimal B/H compared to multi-pass approaches. An alternative 3D2 variant combines and backward strip-map observations from adjacent orbits separated by three days to further refine the B/H ratio when higher precision is required. This observation strategy supports key applications in digital elevation modeling (DEM), particularly for disaster risk assessment—such as evaluating flood-prone areas or hazards—and broad topographic mapping to update national geospatial databases. The resulting DEMs achieve a vertical accuracy of 2.5 m at 1 sigma (with ground control points) for the panchromatic band, enabling reliable height measurements. Operational parameters emphasize a 70 km swath width per , ensuring efficient coverage while prioritizing the panchromatic (0.52–0.77 μm wavelength, 0.8 m ground sample distance) for precise disparity matching in stereo processing. This focus on high-resolution panchromatic data minimizes matching errors, supporting robust even in varied terrains.

Pointing observation mode

The Pointing observation mode of ALOS-3 enables agile off- pointing up to ±60 degrees in all directions from , facilitating targeted imaging of specific areas through slew maneuvers that adjust the satellite's orientation for precise alignment. This capability allows observation of any given point within within 24 hours of receiving a request, leveraging the satellite's reaction wheel-based attitude control system for rapid repositioning without altering the orbital path. Designed primarily for scenarios, this mode supports rapid response to dynamic events such as wildfires or damage from natural disasters, enabling timely data acquisition to inform mitigation efforts. It offers enhanced revisit flexibility for high-priority sites, allowing follow-up observations beyond the nominal 35-day repeat cycle when integrated with ground tasking protocols that prioritize urgent areas. Operational parameters include an adjustable swath width of up to 70 km at for both panchromatic (0.8 m ) and multispectral (3.2 m ) imaging, ensuring coverage tailored to the targeted area's scale while maintaining high-resolution detail. This mode is activated exclusively for emergency observations, distinguishing it from routine systematic acquisitions by emphasizing on-demand, event-driven pointing over fixed-path surveys.

Wide-area observation mode

The wide-area observation mode of ALOS-3 facilitates the acquisition of imagery over extensive regions exceeding 200 km in the along-track direction by 100 km in the cross-track direction, achieved through multiple scan observations during a single orbital path. This approach leverages the satellite's agile pointing capability of up to 60 degrees to capture overlapping strips from the Wide-swath and High-resolution Imager (WISH), enabling the mosaicking of data into a comprehensive wide-area image without requiring multiple orbital revolutions. Key parameters for this mode include a sampling distance of 0.8 m in panchromatic mode and 3.2 m in multispectral mode across six bands (coastal, blue, green, red, red edge, and near-infrared), with an 11-bit quantization for enhanced dynamic range. The nominal swath width per scan is 70 km at , but the pointing maneuver extends effective coverage by combining adjacent observations, prioritizing broad spatial extent over single-pass linear strips. Primarily designed for emergency and large-scale applications, this mode supports regional disaster overviews, such as assessing damage paths or impacts over hundreds of kilometers, as well as environmental surveys for changes and resource mapping. For example, it enables timely monitoring of vast affected areas during events like the hypothetical scenario, providing geospatial data for rapid response and recovery planning.

Changing direction observation mode

The changing direction observation mode of ALOS-3 enables continuous imaging of areas off the satellite's nominal by dynamically adjusting the spacecraft's during a single orbital pass. This mode involves control of the satellite's to redirect the optical , allowing for extended coverage of non-nadir paths without interruption. By continuously repointing the instrument, ALOS-3 can track and image moving or elongated targets, such as expanding zones or vessel convoys, while maintaining image quality through seamless stitching of adjacent swaths. This capability is particularly valuable for monitoring dynamic environmental or human-induced phenomena that evolve rapidly, including riverine floods that alter shorelines or maritime traffic requiring persistent . For instance, during scenarios, the mode facilitates the acquisition of time-sensitive data over irregular or shifting areas, supporting applications in and resource tracking. The pointing agility limits, as utilized in the pointing observation mode, underpin these adjustments, ensuring responsive coverage within operational constraints. Key parameters include a pointing range of up to 60 degrees in all directions from , which allows for flexible off-track observation while preserving an effective swath width of 70 km through ongoing . This configuration supports along-track extensions up to several hundred kilometers in a single pass, optimized for high-resolution panchromatic and without compromising geometric accuracy.

References

  1. [1]
    Advanced Land Observing Satellite-3 “DAICHI-3” (ALOS-3) - JAXA
    The sensor onboard ALOS-3 is designed for an improved ground resolution (0.8 m) and wide-swath (70 km) simultaneously by expanding the size and upgrading ...
  2. [2]
    Launch Failure of the First H3 Launch Vehicle and Setting up ... - JAXA
    Mar 7, 2023 · Then, at 10:51:50, we sent a command destruct signal, effecting a failed launch. We would like to express our deepest apology to many people and ...
  3. [3]
    ALOS-3 (Advanced Land Observing Satellite-3) - eoPortal
    Mar 7, 2023 · Launched on 7 March 2023, Advanced Land Observing Satellite-3 (ALOS-3), also known as Daichi-3, was a follow-on mission from the ALOS/Daichi program.
  4. [4]
    ALOS 3 (Daichi 3) - Gunter's Space Page
    Jun 2, 2025 · JAXA's ALOS 3 (Advanced Land Observation Satellite 3) was an optical Earth observation satellite to be used for cartography, regional observation, disaster ...
  5. [5]
    Outline of advanced land observing satellite-3 and its instruments
    The Japan Aerospace Exploration Agency (JAXA) is planning a satellite system for the Advanced Land Observing Satellite (ALOS) "Daichi" follow-on program.
  6. [6]
    [PDF] JAXA's Earth Observation Mission
    previously carried out by ALOS. (ended operations in May 2011). Advanced Land Observation. Satellite-3 (ALOS-3) (Launch: Scheduled for FY2015 or later). To take ...Missing: milestones announcement
  7. [7]
    A review of Japan's space policy after the H3 launch vehicle failure
    Jun 5, 2023 · The ALOS-3 satellite was initially planned to cost about 38 billion yen to develop, and the H-2A was scheduled to be its launch vehicle.
  8. [8]
    JAXA President Monthly Press Conference January 2019
    Jan 8, 2019 · Likewise, the sum of \8.9 billion funds the development costs of Advanced Optical Satellites-3 and -4, (ALOS-3 and ALOS-4) both slated for ...<|separator|>
  9. [9]
    JAXA President Monthly Press Conference January 2020
    Also, 14.9 billion yen including the supplementary budget has been appropriated to fund the development costs of Advanced Optical Satellite (ALOS-3), a payload ...
  10. [10]
    Japan launches an advanced Earth observation satellite on its new ...
    Jul 1, 2024 · Japan deployed an upgraded Earth observation satellite for disaster response and security after it was launched on a new flagship H3 rocket ...
  11. [11]
    Update of ALOS-3 Calibration and Validation Preparation Status
    The mission objectives of ALOS-3 are (1) to contribute safe and secure social including provision for natural disasters, and (2) to create and update ...
  12. [12]
    Overview of the Japanese Advanced Optical Satellite: mission ...
    Sep 29, 2017 · The main objectives of the ALOS-3 project are to take images of the global land area with high GSD (<1 m) and wide swath (>70 km), and build a ...<|control11|><|separator|>
  13. [13]
    ALOS-3 | ALOS@EORC - JAXA Earth Observation Research
    Advanced Land Observing Satellite-3 (ALOS-3) ; Orbit · Altitude, 669 km at the equator ; Orbit · Local Sun Time, 10:30 am +/- 15 minutes at the descending node.
  14. [14]
    [PDF] appendix 5 overview of the advanced optical satellite (alos-3) mission
    The details are as follows. ALOS-3 can normally perform observation covering 70 km in width and 4,000 km in along-track direction as the stripmap observation ...
  15. [15]
    ALOS-3 - JAXA Earth Observation Research
    The combination of a sensor with a ground resolution of 0.8m and an observation width of 70km is one of the major features of ALOS-3. Off-axis four-mirror ...Missing: prototype testing 2018 2020
  16. [16]
    CALIBRATION AND VALIDATION OF THE ADVANCED LAND ...
    ... radiometric accuracy is ± 10 % as absolutely and ± 5 % as relatively ... 3 “ALOS-3”, Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLIII-B1 ...
  17. [17]
    H3 Launch Vehicle - JAXA
    The H3 Launch Vehicle aims at achieving three factors namely, high flexibility, high reliability, and high cost performance.Missing: 2024 | Show results with:2024
  18. [18]
    Launch Schedule of Advanced Land Observing Satellite-3 ... - JAXA
    Dec 23, 2022 · Launch Schedule of Advanced Land Observing Satellite-3 “DAICHI-3” (ALOS-3) aboard the first H3 Launch Vehicle (H3 TF1). ; : February 12, 2023 · : ...Missing: announcement approval
  19. [19]
    H3 TF-1 (H3-22S) - Tanegashima LC-Y2 - 7 March 2023 (01:37 UTC)
    Sep 8, 2021 · The @JAXA_en ALOS-3 optical Earth observation satellite, payload for the 1st flight of the H3 rocket, arrives at Tanegashima by ship today:Missing: preparation integration
  20. [20]
    Japan's flagship H3 rocket fails on first test flight - Spaceflight Now
    Mar 7, 2023 · JAXA said range controllers sent a destruct command to the rocket after determining there was “no possibility of achieving the mission.” Debris ...
  21. [21]
    [PDF] Conclusion of the H3 Launch Vehicle Test Flight No.1 Failure ...
    Oct 26, 2023 · Three scenarios were extracted as possible failure scenarios, and decision was made to implement measures to address all potential causes ...Missing: LE- 9 crack cooling panel
  22. [22]
    H3 reaches orbit on second launch - SpaceNews
    Feb 16, 2024 · Japan's H3 rocket successfully reached orbit on its second launch Feb. 16, nearly a year after its inaugural launch failed.
  23. [23]
    [PDF] ALOS 2/3の概要について - JAXA Earth Observation Research
    May 25, 2012 · Right or left-looking by spacecraft maneuvering at 30 degrees off-nadir ... ALOS-3 enables to direct the sensor's view to any points in a wide ...
  24. [24]
    https://spaceflightnow.com/2023/03/07/japans-flagship-h3-rocket-fails-on-first-test-flight/
  25. [25]
    [PDF] Advanced Optical Satellite (ALOS-3) Overviews
    Jan 30, 2018 · This mode can cover in wide-ranging area of 200 km (in along- track direction) x 100 km (in cross-track direction) by satellite's single ...
  26. [26]
    [PDF] Advanced Land Observing Satellite (ALOS-3) Update
    ALOS-3 has capability of high GSD (0.8 m) and large field of view (> 70 km) simultaneously. • ALOS-3 image data contributes to.
  27. [27]
    [PDF] ｽﾗｲﾄﾞ ﾀｲﾄﾙなし - Committee on Earth Observation Satellites
    Sep 6, 2018 · JAXA's EO program and status introduced: ✓ GCOM-C is in orbit, and GOSAT-2 will be soon,. ✓ ALOS-2 is working well; Global mosaic production ...