Hiroki Hihara

SpaceWire-based thermal-infrared imager system for asteroid sample return mission HAYABUSA2

Abstract A thermal-infrared (TIR) imager system is developed for HAYABUSA2, which is planned to be launched in 2014 and aims at sample-return from a C-class near-Earth asteroid 162173 (1999JU3) considered to contain organic or hydrated materials. The system consists of a TIR imager and digital electronics, which are used not only for the scientific investigation of physical properties of the asteroid surface, but also for the assessment of landing site selection and safe descent operation onto the asteroid surface with in situ measurement. TIR adopts an uncooled bolometer. Image operations such as multiple images summation, dark image subtraction, and the compensation of dead pixels are processed onboard. A processing module is connected to sensor interfaces through SpaceWire in order to provide deterministic processing time. Data compression is also provided to reduce the restriction of transmission time, which provides the equivalent compression ratio as JPEG2000 in 1 / 30 processing time in average. A high-speed data recorder is connected through SpaceWire in order to record TIR data in parallel with other sensor data. The modularity of SpaceWire enables us to use these as built devices for TIR and inherits the same design as the long-wavelength infrared imager developed for the Venus climate orbiter Akatsuki.

A fast progressive lossless image compression method for space and satellite images

This paper presents a fast lossless image compression method for space and satellite images. The method, which we call HIREW, is based on hierarchical interpolating prediction and adaptive Golomb-Rice coding, and achieves 7-35 times faster compression than existing methods such as JPEG2000 and JPEG-LS, at similar compression ratios. Additionally, unlike JPEG-LS, it supports additional features such as progressive decompression using resolution scaling. An implementation of this codec will be used in the Japan Aerospace Exploration Agency (JAXA)s Venus Climate Orbiter mission (PLANET-C).

Fast Compression Implementation for Hyperspectral Sensor

Fast and small foot print lossless image compressors aiming at hyper-spectral sensor for the earth observation satellite have been developed. Since more than one hundred channels are required for hyper-spectral sensors on optical observation satellites, fast compression algorithm with small foot print implementation is essential for reducing encoder size and weight resulting in realizing light-weight and small-size sensor system. The image compression method should have low complexity in order to reduce size and weight of the sensor signal processing unit, power consumption and fabrication cost. Coding efficiency and compression speed enables enlargement of the capacity of signal compression channels, which resulted in reducing signal compression channels onboard by multiplexing sensor signal channels into reduced number of compression channels. The employed method is based on FELICS1, which is hierarchical predictive coding method with resolution scaling. To improve FELICSs performance of image decorrelation and entropy coding, we applied two-dimensional interpolation prediction and adaptive Golomb-Rice coding, which enables small footprint. It supports progressive decompression using resolution scaling, whilst still delivering superior performance as measured by speed and complexity. The small footprint circuitry is embedded into the hyper-spectral sensor data formatter. In consequence, lossless compression function has been added without additional size and weight.

The SpaceWire-based thermal infrared imager system for asteroid sample return mission HAYABUSA2

Thermal infrared imager system is developed for HAYABUSA2, which is planned to be launched in 2014 and aims at sample-return from a C class near-Earth asteroid 1999JU3 considered to contain organic or hydrated materials. The system consists of a thermal-infrared imager (TIR) and a digital electronics, which is used not only for the scientific investigation of physical properties of the asteroid surface, but also for the assessment of landing site selection and safe descent operation onto the asteroid surface with in situ measurement. Since round trip communication time between the asteroid and the Earth is more than thirty minutes, onboard automatic data processing function and high speed data recording capability are provided to exploit the limited downlink capacity which is up to 32kbps. TIR adopts an uncooled bolometer with 320 x 240 effective pixels. Image operations as multiple images summation, dark image subtraction, and the compensation of dead pixels are processed onboard. A processing module is connected to sensor interfaces through SpaceWire in order to provide deterministic processing time. Data compression is also provided to reduce restriction on storage capacity and operation time, which provides the equivalent compression ratio as JPEG2000 in 1/30 processing time in average. A high speed data recorder is also connected through SpaceWire in 50Mbps in order to record TIR data in parallel with other sensor data. The modularity of SpaceWire enables to use as built devices for TIR and inherits the same design as the long-wavelength infrared imager developed for the Venus climate orbiter Akatsuki.

Development of onboard fast lossless compressors for multi and hyperspectral sensors

Fast and small-footprint lossless compressors for multi and hyper-spectral sensors have been developed. The compressors are employed for HISUI (Hyper-spectral Imager SUIte: the next Japanese earth observation project that will be on board ALOS-3). By using spectral correlations, the compressor achieved the throughput of 30Mpel/sec for hyper-spectral images and 34Mpel/sec for multi-spectral images, which covers the data acquisition throughput of HISUI, on a radiation tolerant FPGA (field-programmable-gated-array). We also implemented the compressor on the evaluation model device of HISUI, and confirmed its feasibility and compression performance of actual hyper-spectral sensor data.

Novel processor architecture for onboard infrared sensors

Infrared sensor system is a major concern for inter-planetary missions that investigate the nature and the formation processes of planets and asteroids. The infrared sensor system requires signal preprocessing functions that compensate for the intensity of infrared image sensors to get high quality data and high compression ratio through the limited capacity of transmission channels towards ground stations. For those implementations, combinations of Field Programmable Gate Arrays (FPGAs) and microprocessors are employed by AKATSUKI, the Venus Climate Orbiter, and HAYABUSA2, the asteroid probe. On the other hand, much smaller size and lower power consumption are demanded for future missions to accommodate more sensors. To fulfill this future demand, we developed a novel processor architecture which consists of reconfigurable cluster cores and programmable-logic cells with complementary atom switches. The complementary atom switches enable hardware programming without configuration memories, and thus soft-error on logic circuit connection is completely eliminated. This is a noteworthy advantage for space applications which cannot be found in conventional re-writable FPGAs. Almost one-tenth of lower power consumption is expected compared to conventional re-writable FPGAs because of the elimination of configuration memories. The proposed processor architecture can be reconfigured by behavioral synthesis with higher level language specification. Consequently, compensation functions are implemented in a single chip without accommodating program memories, which is accompanied with conventional microprocessors, while maintaining the comparable performance. This enables us to embed a processor element on each infrared signal detector output channel.

Infrared sensor system using robotics technology for inter-planetary mission

Infrared sensor system is a major concern for inter-planetary missions in order to investigate the nature and the formation processes of planets and asteroids. Since it takes long time for the communication of inter-planetary probes, automatic and autonomous functions are essential for provisioning observation sequence including the setup procedures of peripheral equipment. Robotics technology which has been adopted on HAYABUSA2 asteroid probe provides functions for setting up onboard equipment, sensor signal calibration, and post signal processing. HAYABUSA2 was launched successfully in 2014 for the exploration of C class near-Earth asteroid 162173 (1999JU3). An optical navigation camera with telephoto lens (ONC-T), a thermal-infrared imager (TIR), and a near infrared spectrometer (NIRS3) have been developed for the observation of geology, thermo-physical properties, and organic or hydrated materials on the asteroid. ONC-T and TIR are used for those scientific purposes as well as assessment of landing site selection and safe descent operation onto the asteroid surface for sample acquisition. NIRS3 is used to characterize the mineralogy of the asteroid surface by observing the 3-micron band, where the particular diagnostic absorption features due to hydrated minerals appear. Modifications were required in order to apply robotics technology for the probe due to the difference of operation on satellites from robot operation environment. The major difference is time line consideration, because the standardized robotics operation software development system is based on event driven framework. The consistency between the framework of time line and event driven scheme was established for the automatic and autonomous operation for HAYABUSA2.

Design of the time assignment system for ASTRO-H and its performance before launch

The ASTRO-H, which will be launched in 2015, is the sixth in a series of Japanese X-ray satellites. It is an international mission led by JAXA in collaboration with NASA and ESA, aiming to observe astrophysical objects in the X-ray band from 0.5 to 600 keV. One of the important scientific goals is to understand physical processes in the extreme environments of active and variable astrophysical objects, such as black holes, neutron stars, binary star, and active galactic nuclei. Therefore, a fast timing capability is a key requirement for the mission. According to numerical estimates of scientific performance, absolute times of X-ray events are required to have an accuracy of 300 μs to achieve minimum scientific goals and an accuracy of 30 μs is desired as a goal. The satellite carries a GPS receiver to get the accurate time information, which is distributed from the central computer on board through the large-and-complex SpaceWire network. Distributions of time information are shared in the same lines used for communications of telemetry and commands, and thus propagation delays and jitters affect the timing accuracy of the payload instruments. Further six items are identified as sources of timing errors and are measured on ground to be used in the calibration by off-line software. The time-assignment tasks in the off-line software packages are designed to be common for all the scientific instruments, although the hardware designs for finer timing resolutions are different by the instruments. Measurements of propagation delays in the flight configuration on ground and in-orbit calibration plans are described. The detail description will be submitted to the IEEE TNS paper in near future. This work demonstrates a good example of care points for space-use instruments in the hardware-and-software designs and calibration measurements in order to achieve a fine timing resolution at the micro second order with the middle-sized satellites using the SpaceWire (IEEE1355) network.

Onboard infrared signal processing system for asteroid sample return mission HAYABUSA2

Onboard signal processing system for infrared sensors has been developed for HAYABUSA2 for the exploration of C class near-Earth asteroid 162173 (1999JU3), which is planned to be launched in 2014. An optical navigation camera with telephoto lens (ONC-T), a thermal-infrared imager (TIR), and a near infrared spectrometer (NIRS3) have been developed for the observation of geology, thermo-physical properties, and organic or hydrated materials on the asteroid. ONC-T and TIR are used for those scientific purposes as well as assessment of landing site selection and safe descent operation onto the asteroid surface for sample acquisition. NIRS3 is used to characterize the mineralogy of the asteroid surface by observing the 3-micron band, where the particular diagnostic absorption features due to hydrated minerals appear. Since the processing cycle of these sensors are independent, data processing, formatting and recording are processed in parallel. In order to provide the functions within the resource limitation of deep space mission, automatic packet routing function is realized in one chip router with SpaceWire standard. Thanks to the SpaceWire upper layer protocol (remote memory access protocol: RMAP), the variable length file system operation function can be delegated to the data recorder from the CPU module of the digital electronics of the sensor system. In consequence the infrared spectrometer data from NIRS3 is recorded in parallel with the infrared image sensors. High speed image compression algorithm is also developed for both lossless and lossy image compression in order to eliminate additional hardware resource while maintaining the JPEG2000 equivalent image quality.

Thermal-IR imaging of a near-Earth asteroid

The Japan Aerospace Exploration Agency/Institute of Space and Astronautical Science Hayabusa2 mission (see Figure 1) is due to be launched in 2014 with the aim of returning a sample from the C-type (rich in carbon) near-Earth asteroid 1999JU3, which is thought to contain organic or hydrated materials.1 A thermal emission map of the asteroid’s surface can be derived from regional variations in measurements of thermal inertia. These measurements provide information about the physical properties of the surface (i.e., whether sand, pebble, or boulder-sized materials are present) and will be used to identify a suitable landing site. Hayabusa2 is a follow-up to the Hayabusa probe that performed the first round trip, with sample return, to an asteroid in 2010. The Hayabusa2 spacecraft design builds on the heritage of Hayabusa, but includes several refinements. Although the primary goal of the mission is to return a sample of the asteroid, remote sensing of the body is also an important aspect. The physical properties and composition of the uppermost layer of the asteroid will be investigated in an active impact experiment where the small carry-on impactor instrument will form a crater (a few to several meters in diameter) and excavate parts of the subsurface. The crater and surrounding ejecta will be studied with an optimized set of remote sensing instruments that include multi-band telescopic and wide-angle imagers, a laser ranger (lidar), a near-IR spectrometer (to detect an absorption band at 3 m characteristic of water ice or hydrated minerals), and a thermal-IR imager (TIR). With these sensors, the mid-IR thermal emission and surface temperature profiles of the asteroid will be acquired, as well as their temporal variation with the asteroid’s rotation. Our TIR instrument is based on the design of the longwavelength IR imager that was built for the Venus climate mission Akatsuki.2, 3 It has been adapted to meet the Hayabusa2 Figure 1. An artist’s impression of the Hayabusa2 probe’s encounter with a near-Earth asteroid. ( c Akihiro Ikeshita.)