2017-3-14 0.6 version 0.6

HAYABUSA2 Optical Navigation Camera(ONC)

Instrument Overview

The optical navigation camera (ONC) system onboard the Hayabusa2 spacecraft consists of one telescopic camera (T) and two wide-angle cameras (W1 and W2).

The ONC-T is a telescopic camera with seven band-pass filters in the visible and near-infrared range. These filters are placed on a wheel, which rotates to put a selected filter for different observations, enabling multiband imaging.

The main objective of this instrument is to optically navigate the spacecraft to asteroid Ryugu (1999 JU3) and to conduct muti-band mapping the asteroid for choosing touchdown cand idate sites and understanding the nature of this asteroid.

Contents

Definition of Product Level

File Naming Convention

Data Processing tools

Calibration (in preparation)

(1) Alignment Offset

The Alighment offset (deviation of the optical axis from the center of the image might be also included) is summarized as table 1 ( see Suzuki et al. (2017)) .

Table 1. Optical axis offset for W1, W2 and T
W1 W2 T
dx [pixel] -4.1 0(<1) 11.4+-0.6
dy [pixel] -2.7 0(<1) -22.0+-0.7

(2) Distortion Correction

Suppose the pixel at the position (x, y) in the image is projected to the point (x', y') after the distortion correction (the origin is defined to be the center of the image). The distance of the pixel from the center of the image is denoted by r = sqrt(x ^2+y^2).

The projection relation of the point with the distance r to the point with the distance r' is given by

r'=L_1 r+L_2 r^3+L_3 r^5, (1)

where L1, L2 and L3 are parameters for distortion correction defined for each camera. Then the pixel positions without distortion is calculated by the following equation (2):

x'= (r'/r)x , y'= (r'/r)y. (2)

The parameters in the above equations (1) and (2) obtained for W1, W2 and T are listed in Table 1. The details of the calibration using the star-field images are described in the paper by Suzuki et al. (2017).

Table 1 Parameters obtained for distortion correction for W1, W2 and T
W1 W2 T
L_1 1.027 1.014 1
L_2 3.219E-7 2.933E-7 -9.28E-9
L_3 -1.762E-13 -1.384E-13 0
RMS Error [pixels]
(after correction)
0.6 0.5 0.16

(3) Radiometric Correction

In preparation (see Kameda et al. (2016) and Suzuki et al.(2017)).

Definition of Mission Phase

2014/12/03-2015/12/03 EDVEGA (Electric Delta-V Earth Gravity Assist).
From launch until Earth swing-by.
2015/12/03-2018/06/** Transfer

Reference