APPENDIX 7
OVERVIEW OF
THE MULTI-FOOTPRINT OBSERVATION LIDAR AND
IMAGER(MOLI) MISSION7-1

1. Introduction
Forest biomass is the dry weight of trees, and half of which is carbon weight, therefore it is frequently used as aunit to evaluate carbon stocks in forests. Also, canopy height is one of the quantitative parameters of forest which
can be measured relatively easily, and it is correlated with forest biomass. Meanwhile, in recent years, the necessity
to measure forest carbon stocks has increased in relation to the climate change. In this context, demand for canopy
height and forest biomass measurement technology is increasing significantly.
Among many satellite sensors, the Light Detection and Ranging (LiDAR) is the most accurate one capable ofmeasuring those forest parameters. As shown in Figure 1, spaceborne LiDAR irradiates the ground surface withlaser beam, and observes the waveform of reflected beam. Analyzing such waveform makes us possible to estimate
the canopy height and the above-ground biomass (AGB) of forests. NASA's ICESat/GLAS, operated from 2003 to2009, was the only spaceborne LiDAR to observe the Earth's surface so far. NASA will start to operate twospaceborne LiDAR missions i.e. ICESat-2/ATLAS and GEDI. In addition to these missions, the Multi-footprint
Observation Lidar and Imager (MOLI) is expected to contribute to the semi-global forest observation.

← TimeBin番号500

400300

信号開始
200100

信号終了
0050

100150反射レーザ
Reflectance
反射レーザ

Figure 1 Schematic chart of spaceborne LiDAR observation.

2. Mission Objectives of MOLIMOLI will provide accurate observation data of forest biomass on semi-global scale, and its objectives are toreduce the uncertainty of forest carbon budget in the carbon cycle process, and to contribute as a monitoring tool
for the REDD+ scheme, which is one of measures against climate change. Regarding the former objective, terrestrial
ecosystems (chiefly forests) have the largest uncertainty in the carbon cycle process, so accurate information offorest biomass (i.e., carbon stocks) distribution can greatly contribute to the progress of understanding it. Regarding
the latter objective, the REDD+ scheme demands developing countries to accurately account forest carbon budget,so MOLI is expected to help them. Furthermore, a secondary objective is to acquire spaceborne laser technology inthe process of development and operation of MOLI instrument, and to make it a preparation for future spaceborne
LiDAR mission.

3. Observation System
MOLI will be installed in the Exposed Facility of the Japanese Experiment Module (JEM) "Kibo" of theInternational Space Station (ISS) around 2021. It has two sensors: LiDAR and imager. Table 1 shows the major
specifications of each sensor. LiDAR, the main sensor, emits two laser beams to place the footprints continuously(Figure 2). When we estimate the canopy height or AGB from spaceborne LiDAR waveform, a pulse broadening
effect by ground slope affects the estimation accuracy significantly. However, MOLI can calculate the ground slope
angle by comparing measured values of ground elevation between adjacent footprints, and it can be used to correct
the pulse broadening effect. This function can be expected to contribute to the improvement of the estimation
accuracy of the canopy height and the above-ground biomass. In addition, the imager makes us possible tounderstand forest conditions around the footprint by shooting at the same time as LiDAR observation, although it
has a narrow observation swath.
7-2

Table 1 Major characteristics of MOLI instruments.
Sensor
LiDAR

ImagerParameter
Laser wavelength
Laser power
Laser pulse frequency
Laser pulse width
Receive telescope aperture
A/D sampling rate
Measurement range
Footprint diameter
Swath
Ground resolution
BandSpecification
1,064 nm
> 40 mJ
150 Hz< 7 nsec
450 mm (TBD)
500 Msps (height resolution = 30 cm)-50 m ～ +4,000 m above ground level (TBD)
25 mΦ
1,000 m
5m
Green, Red, Near Infrared
Along track

50m50mBeam 150m
Beam 2Footprint
25mφ

Figure 2 Distribution of LiDAR footprints of MOLI.

4. Products
MOLI has standard products of Level-1B and 2, and research products of Level-3 and 4 (Table 2). The L1B
LiDAR product contains observed waveform with basic information i.e. geographical coordinates of footprint. TheL2 product contains estimated values of the canopy height and AGB obtained as a result of waveform analysis foreach footprint. Levels 3 and 4 products are the canopy height and AGB map created from combining LiDAR datawith satellite image data. Regarding the image data, L3 uses images acquired by the MOLI imager, and L4 uses
images acquired by other satellites i.e. ALOS-4/PALSAR-3 or GCOM-C/SGLI. Levels 3 and 4 products use L2
canopy height data and L2 AGB data as training data and validation data.
Table 2 MOLI products (under designed).
Level
1B
2

Data source
LiDAR
ImagerProduct
Waveform data
Ortho-rectified image

LiDAR

Canopy height
Above-ground biomass (AGB)

3LiDAR, Imager

4LiDAR, othersatellite imageAlong-track canopy height map
Along-track AGB map
Large-scale canopy heightmap
Large-scale AGB map

Note: target area is under 30° of ground slope.

7-3

Specification
Alignment accuracy: < 2 pixels
Accuracy: < 3 m (@ canopy height < 15 m) /< 25% (@ canopy height > 15 m)
Accuracy: < 20 Mg ha-1 (@ AGB < 100 Mgha-1) / < 25% (@ AGB > 100 Mg ha-1)
Swath: 1,000 m,
Ground resolution: < 100 m
Ground resolution: < 250 m