Accurate measurements of above ground biomass are important to evaluate its contribution as a CO2 absorption source. If global canopy height model can be obtained, we can make an appropriate evaluation. This is MOLI’s mission. Moreover, MOLI can improve the accuracy of digital terrain model. In this paper, we will report on the development status of MOLI for LIDAR observation from space by mounting on the Japanese Experiment Module with International Space Station.
Accurate measurements of forest biomass are important to evaluate its contribution as a source of CO2 absorption. Forest biomass correlates with forest canopy height, and thus global measurements of canopy heights lead to a better understanding of the global carbon cycle. Space-borne lidar has the unique capability of measuring forest canopy height. A vegetation lidar named MOLI (Multi-footprint Observation Lidar and Imager) has been designed to observe canopy heights more accurately, and MOLI is currently being studied in the Japan Aerospace Exploration Agency (JAXA). This paper introduces an overview of MOLI and its current status.
Accurate measurements of forest biomass are important to evaluate its contribution to the global carbon cycle. Forest biomass correlates with forest canopy height; therefore, global measurements of canopy height enable a more precise understanding of the global carbon cycle. A vegetation lidar named “MOLI” which is designed to measure accurate canopy height has been studied by the Japan Aerospace Exploration Agency (JAXA) in cooperation with some researchers. MOLI stands for Multi-footprint Observation Lidar and Imager.
The feature of MOLI is to set multi-footprints for improving the precision of canopy height, and we can find out whether ground surface is flat or slope because an angle of inclination affects the estimation of canopy height.
MOLI is going to be mounted on the Exposed Facility (EF) of the Japanese Experiment Module (JEM, also known as “Kibo”) on the International Space Station (ISS). Now, we are carrying out a feasibility study and some experiments. We introduce an overview and a status of MOLI.
We carried out various tests of 800-mm-diameter aperture, lightweight optics that consisted wholly of carbon fiber-reinforced SiC composite, called HB-Cesic. A cryogenic optical test was performed on the primary mirror to examine any CTE irregularity as a surface change, and only small deformations were observed. The primary mirror was assembled with a convex secondary mirror into an optical system and tested under vacuum at the 6-m-diameter radiometer space chamber at Tsukuba Space Center of JAXA, where we have prepared interferometric metrological facilities to establish techniques to test large optical systems in a horizontal light-axis configuration. The wavefront difference between under vacuum and under atmosphere was confirmed to be less than 0.1 λ at λ=633 nm, if we realigned the optical axis of the interferometer and flat mirror under vacuum. We also demonstrated a stitching interferometry using the Φ800-mm optics by rotating a mask wheel of subapertures in front of the optical reference flat. The wavefront stitched from eight individual measurements of Φ275-mm subapertures differs from the full-aperture measurement without the mask by about 0.1 λ nm RMS, which showed the technique could able to be applied to test large telescopes especially for infrared wavelength region.
A large-scale lightweight mirror that is made of silicon carbide-based material is required for the coming astronomical and earth observation missions. The influence of the inhomogeneity of the coefficient of thermal expansion (CTE) on specular surface accuracy was studied as an important technological issue for such a large optical component. At first, a systematic case study for the series of CTE’s main factors was conducted using the finite element method, and consequently a comprehensive equation to calculate the amount of surface deviation was derived. Based on that technology, finite element analysis to simulate the surface accuracy profile that a test mirror sample showed during cryogenic measurement was carried out using experimentally obtained CTE data from cutout test pieces, and the profile was successfully reproduced.
Multi-footprint Observation LIDAR and Imager (MOLI) is a candidate mission for International Space Station – Japanese Experiment Module. The mission objective MOLI is to manage forest and to be a good calibrator for evaluation of forest biomass using satellite instrument such as L-band SAR. SAR is the powerful tool to evaluate biomass globally. However it has some signal saturation over 100 t/ha biomass measurement, whereas Vegetation LIDAR is expected to measure higher mass precisely. MOLI is designed to evaluate forest biomass with high accuracy. An imager, that is equipped together in good registration with LIDAR, will help to understand the situation of target forest. Also two simultaneous Laser beams from MOLI will calibrate the relief effect, which affects the precision of canopy height extremely. Using together with L-band SAR observation data or multispectral image, it is expected to have a good “wall to wall” biomass map with its phonological information. Such MOLI observation capability is so important, because both quantity and quality evaluation of biomass are essential for carbon circulation system understandings. Currently, as a key technical development, LASER Transmitters for MOLI is under test in vacuum condition. Its power is 40mJ and PRF is 150Hz. Pressure vessel design for LIDAR transmitter is supressing Laser induced contamination effect. MOLI is now under study towards around 2020 operation.
Accurate measurements of forest biomass are important to evaluate its contribution to the global carbon cycle. Forest
biomass correlates with forest canopy height; therefore, global measurements of canopy height enable a more precise
understanding of the global carbon cycle. Space-borne lidar has the unique capability of measuring forest canopy height.
A vegetation lidar named Multi-footprint Observation Lidar and Imager (MOLI) has been designed to make accurate
measurements of canopy height and is currently being studied in the Japan Aerospace Exploration Agency. This papers
introduces an overview of MOLI and its current status.
IPCC Fifth Assessment Report says that there are still large uncertainties of carbon flux estimations in the interaction between ground and atmosphere. That is because of the uncertainties of “change of land use”, in other words, “change of biomass” such as deforestation. Biomass estimation needs not only area of the forest but also its height information with topological features. In that sense, active sensors are highly expected for precise height measurement. Laser Altimeter or simply LIDAR is able to measure the height of dense forest, where SAR has salutation. ICESat / GLAS is firstly used to measure biomass as satellite LIDAR. However it was reported that there is uncertainty where terrain relief exists. To calibrate terrain relief using multi footprints, a Vegetation LIDAR named MOLI (Multi Observation LIDAR and Imager) was studied by JAXA. The unique points of MOLI are the dual beams with enough small and close footprints to determine terrain relief. Full wave analysis technique is also under development to distinguish canopy heights, crown depth and other forest features. Co-aligned imager will be used for determination of positions where LIDAR measured and observation of phonology. MOLI system design is about to finalize. Regarding Laser Transmitter, Bread Board Model with pressure vessel is being tested under vacuum condition. Target launch year of MOLI is around 2019.
An uncooled infrared (IR) focal plane array (FPA) with 23.5 μm pixel pitch has been successfully demonstrated and has found wide commercial applications in the areas of thermography, security cameras, and other applications. One of the key issues for uncooled IRFPA technology is to shrink the pixel pitch because the size of the pixel pitch determines the overall size of the FPA, which, in turn, determines the cost of the IR camera products. This paper proposes an innovative pixel structure with a diaphragm and beams placed in different levels to realize an uncooled IRFPA with smaller pixel pitch (≦17 μm ). The upper level consists of a diaphragm with VO x bolometer and IR absorber layers, while the lower level consists of the two beams, which are designed to be placed on the adjacent pixels. The test devices of this pixel design with 12, 15, and 17 μm pitch have been fabricated on the Si read-out integrated circuit (ROIC) of quarter video graphics array (QVGA) (320×240 ) with 23.5 μm pitch. Their performances are nearly equal to those of the IRFPA with 23.5 μm pitch. For example, a noise equivalent temperature difference of 12 μm pixel is 63.1 mK for F/1 optics with the thermal time constant of 14.5 ms. Then, the proposed structure is shown to be effective for the existing IRFPA with 23.5 μm pitch because of the improvements in IR sensitivity. Furthermore, the advanced pixel structure that has the beams composed of two levels are demonstrated to be realizable.
Vegetation LIDAR, which measures an accurate canopy height, has been studied by JAXA. Canopy height is a very important parameter to estimate forest biomass, and global measurement of accurate canopy height leads to better understanding of the global carbon cycle. The vegetation LiDAR is designed based on the assumption that it is to be mounted on the Exposed Facility (EF) of the Japanese Experiment Module (JEM, also known as “Kibo”) on the International Space Station (ISS). The vegetation LIDAR uses an array detector (2x2) for dividing the ground footprint, making it possible to detect the slope of the ground for improving the accuracy of canopy height measurement. However, dividing the footprint may cause a reduction in reflected lights and signal-to-noise ratio (SNR); hence, the vegetation LiDAR system needs high sensitivity and low-noise array detector module. We made a prototype of the array detector module and it satisfied the tentative target SNR which we set. This presentation will introduce the mission objectives, the LiDAR system including experimental prototypes of array detector module, and some results of the study.
Fourier transform spectrometer (FTS) has many advantages, especially for greenhouse gases and air pollution
detection in the atmosphere, because a single instrument can provide wide spectral coverage and high spectral
resolution with highly stabilized instrumental line function for all wavenumbers. Several channels are usually
required to derive the column amount or vertical profile of a target species. Near infrared (NIR) and shortwave
infrared (SWIR) spectral regions are very attractive for remote sensing applications. The GHG and CO of
precursors of air pollution have absorption lines in the SWIR region, and the sensitivity against change in the
amounts in the boundary layer is high enough to measure mole fractions near the Earth surface. One disadvantage
of conventional space-based FTS is the spatial density of effective observation.
To improve the effective numbers of observations, an imaging FTS coupled with a two-dimensional (2D)-camera
was considered. At first, a mercury cadmium telluride (MCT)-based imaging FTS was considered. However, an
MCT-based system requires a calibration source (black body and deep-space view) and a highly accurate and
super-low temperature control system for the MCT detector. As a result, size, weight, and power consumption are
increased and the cost of the instrument becomes too high. To reduce the size, weight, power consumption, and
cost, a commercial 2D indium gallium arsenide (InGaAs) camera can be used to detect SWIR light. To
demonstrate a small imaging SWIR-FTS (IS-FTS), an imaging FTS coupled with a commercial 2D InGaAs camera
was developed. In the demonstration, the CH4 gas cell was equipped with an IS-FTS for the absorber to make the
spectra in the SWIR region. The spectra of CH4 of the IS-FTS demonstration model were then compared with
those of traditional FTS. The spectral agreement between the traditional and IS-FTS instruments was very good.
Owing to its high specific stiffness and high thermal stability, silicon carbide is one of the materials most suitable for large space-borne optics. Technologies for accurate optical measurements of large optics in the vacuum or cryogenic conditions are also indispensable. Within the framework of the large SiC mirror study program led by JAXA, we manufactured an 800-mm-diameter lightweight telescope, all of which is made of HB-Cesic, a new type of carbon-fiber-reinforced silicon carbide (C/SiC) material developed jointly by ECM, Germany and MELCO, Japan. We first fabricated an 800-mm HB-Cesic primary mirror, and measured the cryogenic deformation of the mirror mounted on an HB-Cesic optical bench in a liquid-helium chamber. We observed the cryo-deformation of 110 nm RMS at 18 K with neither appreciable distortion associated with the mirror support nor significant residual deformation after cooling. We then integrated the primary mirror and a high-order aspheric secondary mirror into a telescope. To evaluate its optical performance, we established a measurement system, which consists of an interferometer in a pressure vessel mounted on a 5-axis adjustable stage, a 900-mm auto-collimating flat mirror, and a flat mirror stand with mechanisms of 2-axis tilt adjustment and rotation with respect to the telescope optical axis. We installed the telescope with the measurement system into the JAXA 6-m chamber and tested them at a vacuum pressure to verify that the system has a sufficiently high tolerance against vibrations in the chamber environment. Finally we conducted a preliminary study of sub-aperture stitching interferometry, which is needed for telescopes of our target missions in this study, by replacing the 900-mm flat mirror with a rotating 300-mm flat mirror.
It is very important to watch the spatial distribution of vegetation biomass and changes in biomass over time,
representing invaluable information to improve present assessments and future projections of the terrestrial carbon cycle.
A space lidar is well known as a powerful remote sensing technology for measuring the canopy height accurately. This
paper describes the ISS(International Space Station)-JEM(Japanese Experimental Module)-EF(Exposed Facility) borne
vegetation lidar using a two dimensional array detector in order to reduce the root mean square error (RMSE) of tree
height due to sloped surface.
SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is a Japan-led infrared astronomical satellite project
with a 3.2-m lightweight cryogenic telescope. The SPICA telescope has stringent requirements such as that for the
imaging performance to be diffraction-limited at the shortest core wavelength of 5 microns at the operating temperature
of 6 K. The design of the telescope system has been studied by the Europe-Japan telescope working group led by ESA
with the European industries, the results of which will be presented in other papers. We here present our recent optical
testing activities in Japan for the SPICA telescope, focusing on the experimental and numerical studies of stitching
interferometry. The full pupil of the SPICA telescope will be covered by a sub-pupil array consisting of small
autocollimating flat mirrors (ACFs), which are rotated with respect to the optical axis of the telescope. For preliminary
stitching experiments, we have fabricated an 800-mm lightweight telescope all made of the C/SiC called HBCesic, which
is a candidate mirror material for the SPICA telescope, and started optical testing with 900-mm and 300-mm ACFs at an
ambient temperature. ACFs can suffer significant surface deformation in testing a telescope at cryogenic temperatures,
which is difficult to be measured directly. We therefore investigate the effects of the surface figure errors of the ACFs on
stitching results by numerical simulation.
We report the development of a 2-million-pixel, that is, a 2000 x 1000 array format, SOI diode uncooled IRFPA with 15
μm pixel pitch. The combination of the shrinkable 2-in-1 SOI diode pixel technology, which we proposed last year [1],
and the uncooled IRFPA stitching technology has successfully achieved a 2-million-pixel array format. The chip size is
40.30 mm x 24.75 mm. Ten-series diodes are arranged in a 15 μm pixel. In spite of the increase to 2-million-pixels, a
frame rate of 30 Hz, which is the same frame rate as our former generation (25 μm pixel pitch) VGA IRFPA, can be
supported by the adoption of readout circuits with four outputs. NETDs are designed to be 60 mK (f/1.0, 15 Hz) and 84
mK (f/1.0, 30 Hz), respectively and a τth is designed to be 12 msec. We performed the fabrication of the 2-million-pixel
SOI diode uncooled IRFPAs with 15 μm pixel pitch, and confirmed favorable diode pixel characteristics and IRFPA
operation where the evaluated NETD and τth were 65 mK (f/1.0, 15 Hz) and 12 msec, respectively.
The performance of space-borne infrared detectors is required higher sensitivity, higher resolution, or larger format in
comparison with that of ground-based infrared detectors. In order to realize higher mission requirements, JAXA decided
to position the infrared detector technology as one of the strategic technologies of JAXA and to promote the
development of the infrared detectors.
InAs/GaSb Type II superlattice (T2SL) is the only known infrared material that has a theoretically predicted higher
performance than HgCdTe. If the T2SL detector is realized, it can be applied for high sensitivity infrared sensors, which
are required for many advanced instruments such as an imaging Fourier Transform Spectrometer. The final goal of the
T2SL detector development is to realize an array detector having a cutoff wavelength of λc=15μm.
We have started a basic research on the T2SL detector. In this paper, we report on the first results of the development of
T2SL detectors of mid-wave infrared regime. The detector structure is a pin photodiode with SL of 9 InAs monolayers
(MLs) and 7 GaSb MLs. We present results of optical evaluation of the detector. The cutoff wavelength is 5.5μm at 30K.
The responsivity is 0.33±0.05A/W at 4.5 μm.
Since authors have successfully demonstrated uncooled infrared (IR) focal plane array (FPA) with 23.5 um pixel
pitch, it has been widely utilized for commercial applications such as thermography, security camera and so on. One of
the key issues for uncooled IR detector technology is to shrink the pixel size. The smaller the pixel pitch, the more the IR
camera products become compact and the less cost. This paper proposes a new pixel structure with a diaphragm and
beams which are placed in different level, to realize an uncooled IRFPA with smaller pixel pitch )≤17 μm). The upper
level consists of diaphragm with VOx bolometer and IR absorber layers, while the lower level consists of the two beams,
which are designed to place on the adjacent pixels.
The test devices of this pixel design with 12 um, 15 um and 17 um pitch have been fabricated on the Si ROIC of
QVGA (320 × 240) with 23.5 um pitch. Their performances reveal nearly equal to the IRFPA with 23.5 um pitch. For
example, noise equivalent temperature difference (NETD) of 12 μm pixel is 63.1 mK with thermal time constant of 14.5
msec. In addition, this new structure is expected to be more effective for the existing IRFPA with 23.5 um pitch in order
to improve the IR responsivity.
Scalable new SOI diode structure has been proposed and developed for beyond 17μm pixel pitch mega-pixel-class SOI
diode uncooled infrared focal plane arrays (IRFPAs). Conventionally, each p+n vertical diode is formed between a p+diffusion and an n-body in each SOI active area, and 8-10 diodes are serially connected with interconnections. In the
proposed new structure, we employ two kinds of diodes, namely, p+n and n+p vertical diodes. First, two regions of an nbody
and a p-body are prepared in an SOI active area. In the n-body, a p+ diffusion is formed apart from the n-body /pbody
boundary. In the p-body, an n+ diffusion is formed apart from the boundary. In this way, a p+n vertical diode and an
n+p vertical diode are formed together in an SOI active area. Moreover, a contact hole, which is formed in touch with
both n- and p-bodies, electrically connects these two kinds of diodes. With this new structure which is named "new 2-in-
1 SOI diode structure", we have realized remarkable reduction of the diode area. It leads to significant increase of the
diode series number in a pixel, which increases infrared responsivity of the pixel. As a result, designing a 15μm pixel
pitch IRFPA with the new structure, 12 series diodes can be arranged in a pixel, although 10 series diodes have been
used even in the case of our 25μm pitch generation pixel.
To confirm the ability of the new diodes, test elements of 12-17μm pitch pixels were fabricated and evaluated.
Furthermore, the fabrication of 17μm pixel pitch 320 x 240 IRFPAs with the new diodes was carried out and their
favorable FPA operations were successfully verified.
In conclusion, the proposed and developed new SOI diode technology is very promising for beyond 17μm pixel pitch
mega-pixel-class uncooled IRFPAs.
The Advanced Land Observing Satellite (ALOS) "Daichi," launched in January 2006, has been operating successfully
on orbit for four and a half years. In that time it has delivered a very large number of high-resolution images and has
contributed to making basic maps, updating maps, gathering information on natural resources, and disaster management
support in a variety of fields. The Japan Aerospace Exploration Agency (JAXA) has been planning a satellite system for
the ALOS follow-on program. The ALOS follow-on program consists of two satellites: one is a radar satellite called
ALOS-2, the other is an optical satellite called ALOS-3.
ALOS-3 carries an optical imager with more enhanced capabilities than those of the Panchromatic Remote-sensing
Instrument for Stereo Mapping (PRISM) aboard ALOS. ALOS-3 will produce a precise basic map with its systematic
observation to be used in the Geographical Information System (GIS). ALOS-3 will also promptly provide precise postdisaster
images to detect damaged areas through emergency observations when disasters occur.
JAXA has been defining system requirements for the spacecraft and the mission instrument of ALOS-3, as well as
conducting the conceptual design.
This paper introduces the latest design, the mission concept, and the current status of ALOS-3.
We present a test of optical metrology for 800-mm spaceborne optics in the 6-m radiometer thermal vacuum chamber at
JAXA's Tsukuba Space Center of JAXA. Under the framework of the JAXA's large-optics study program for astronomy
and Earth observations, we developed a test bench for interferometric metrology of large optics with an auto-collimation
method in the chamber. The optical system was aligned in a horizontal light-axis configuration within the facility limit to
handle a 3.5-m aperture telescope like SPICA. A high-speed interferometer was contained in an aluminum and titanmade
pressure vessel, which was mounted on the five-axis stage. We tested the 800-mm lightweight C/SiC optics using a
900-mm diameter flat mirror. Alignment changes in tilts of about ten arcseconds were observed as pressure went down
from 1 atm to vacuum. After we re-aligned the interferometer and flat mirror, the wavefronts through the optics under
vacuum were observed to increase in astigmatism aberration by 0.07λRMS at λ=633nm from under atmosphere, which
might be caused by a deformation in the test optics or flat mirror.
SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is a Japan-led infrared astronomical satellite project
with a 3-m-class telescope in collaboration with Europe. The telescope is cooled down to temperature below 6 K in space
by a combination of mechanical coolers with radiative cooling in space. The telescope has requirements for its total
weight to be lighter than 700 kg and for the imaging performance to be diffraction-limited at 5 μm at 6 K. The mirrors
will be made of silicon carbide (SiC) or its related material, which has large heritages of the AKARI and Herschel
telescopes. The design of the telescope system has been studied by the Europe-Japan telescope working group led by
ESA with European industries to meet the requirements. As for optical testing, responsibilities will be split between
Europe and Japan so that final optical verification at temperatures below 10 K will be executed in Japan. We present our
recent optical testing activities in Japan for the SPICA telescope, which include the numerical and experimental studies
of stitching interferometry as well as modifications of the 6-m-diameter radiometer space chamber facility at Tsukuba
Space Center in JAXA. We also show results of cryogenic optical testing of the 160-mm and 800-mm lightweight
mirrors made of a C/SiC material called HBCesic, which is a candidate mirror material for the SPICA telescope.
A new multi-FOV space-borne lidar named "A-lidar" is being studied by the National Space Development Agency of Japan (NASDA) for the earth radiation mission proposed as a joint program with the European Space Agency (ESA). The mission is named "EarthCARE". It was formerly called ATMOS-B1 or ERM. The lidar has a two-wavelength transmitter (1064 nm and 532 nm), a dual polarization receiver at 1064 nm, and a multi-field-of-view (multi-FOV) receiver at 532 nm. The multi- FOV feature of A-lidar will enable us to solve the multiple scattering problems with space lidar measurements of profiles of clouds and aerosols. The multi-FOV feature can also be used for characterization of aerosols.
A solid state airborne lidar for profiling cloud and aerosol scattering has been demonstrated. The transmitter of the lidar is a laser diode pumped Q-switched Nd:YLF laser. The wavelength of the laser is 1,053 nm, output energy from a transmitter optics is 16.5 mJ and repetition rate is 50pps. Eye safety is obtained through beam expansion, whose divergence is 2.6mrad. The diameter of the telescope made of beryllium is 200mm, the field of view is 0.3mrad. The receiver employs a photon counting solid state Geiger mode avalanche photodiode. The vertical resolution is 75m. The received signals were integrated 300 times to the horizontal direction to improve the signal to noise ratio. The measurements for airmolecule, aerosol and cloud were performed using the lidar in November, 1997. The airplane made a round trip from Nagoya airport to Kashima nada via Tsukuba in Japan. The altitude of the airplane was 6,150 m. The measurements indicate that the lidar is capable of detecting and profiling cloud and aerosol scattering through the atmosphere.
In the Mission Demonstration Satellite Lidar (MDS-lidar) Project, the National Space Development Agency of Japan (NASDA) has started development of a satellite-borne lidar system for experiments in space, which is called Experimental Lidar-In-Space Equipment (ELISE). Its main purposes are to demonstrate technical feasibility of a space-borne lidar and its key components, and also to get scientific data on clouds/aerosols distribution for better understanding of the earth climate system. Presentation will be made on the ELISE development plan, scientific goals and their implementation plan.
The experimental lidar in space equipment (ELISE), one of NASDA's lidar programs, means the two-wavelength backscatter lidar. It is planned to be loaded onto the mission demonstration satellite (MDS)-2 planned to be launched early in 2001. One of the special features of ELISE is to be developed in short period using two models called the Basic Test Model and the demonstration model (DM). Through this program, we try to demonstrate some key devices, such as a lightweight laser diode (LD)-pumped high power LASER, a large diameter telescope an a photon counting detector using silicon avalanche photo diode, which are required for future spaceborn lidars. The experimental data of key devices in the space environment will be obtained. Furthermore, ELISE will observe clouds in the high altitude, multi-layered clouds, aerosols and the atmospheric density through one year. This observation will reveal the scientific value and the availability of spaceborn lidars. The collection of the information on clouds, aerosols and the density will be a great help to the design of future spaceborn lidars.
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