IEEE - Aerospace and Electronic Systems - May 2022 - 34

Hayabusa2 Re-Entry Capsule Tracking by Marine Radars
junction unit included a motor driver, a dc converter, and
a switching hub to connect to the manned-side equipment.
The manned side was where each MRS site's personnel
operated the radar, and all equipment was installed in a
travel trailer. This side consisted of a laptop, an emergency
switch, and a GPS receiver for data-time synchronization.
These were located at least 30 m away from the
radar side to protect them from radio-wave exposure. The
target for azimuth calibration was set on the reflector side.
This target was permanently placed during the recovery
operation and was always used before measurements.
The marine radar stations were deployed at four sites
Figure 9.
Balloon orbit measured by the marine radar (blue) and the radiosonde
at N3 (black).
and the error is changed by the observed distance. However,
because the position error due to azimuth error was
0.9 km at a distance of 35 km, the measurement accuracy
of the marine radar was not considered to be a problem.
RECOVERY OPERATION
EXPLORATION PLAN OF THE MRS
The MRS was designed to use multiple radars in order to
cover the search area based on the detection performance
shown in the previous chapter. Each radar site had the
same configuration and consisted of the same sets of
equipment on the radar side, the manned side, and the
reflector side (see Figure 10). The radar side consisted of
the marine radar, the junction unit, and the battery. The
marine radars were those described previously. The
around the predicted landing point (see Figure 11). However,
an exclusion zone was set in the vicinity ofthe predicted landing
point in case ofa parachute error. The maximum distance
between each site was 44 km. In addition, because there was
no public communication network in the WPA, each site was
tracked individually. The results were aggregated by satellite
phones after the tracking operation. TheMRS was able to estimate
the position at one site, so sharing only the final detection
result was assumed to be enough to contribute a rapid recovery.
Note that N1-C2 and S2 shown in the figure are also
namesofthe respective sitesas wellasN2 andN3.
Each site was set up over two days, nine days before
the re-entry (days R-9 and R-8). In this installation, the
radar position and the azimuth were calibrated using the
GPS receiver and the reflector, respectively.
MEASUREMENT ACCURACY CONFIRMATION
The measurement accuracies were confirmed by tracking
the helicopter on day R-6. The helicopter flew the planned
route, hovering several times (see Figure 12). Each site
tracked the helicopter near its own site. Figure 13 shows
the tracking results from N1-C2 for reference. The accuracies
were confirmed by comparison with the position data
Figure 10.
Equipment configuration ofeach radar site.
34
IEEE A&E SYSTEMS MAGAZINE
MAY 2022
IEEE - Aerospace and Electronic Systems - May 2022

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