14:15 〜 14:30
[PPS03-14] Thermal infrared multiband imager TIRI for S-type potentially hazardous asteroid Didymos in Hera mission
キーワード：プラネタリ―ディフェンス、熱物性、赤外分光観測、ヘラ、小惑星探査
Introduction: TIRI is a bolometer-based thermal infrared imager with an 8-position filter wheel, for the ESA Hera mission [1]. The instrument will be used to investigate thermophysical properties and constituent material composition of the S-type near-Earth binary asteroid 65803 Didymos and its moon Dimorphos. The specifications, performances, and test results, and operation plans of TIRI are reported.
Hera: Hera is the asteroid mission led by ESA [2] and a part of the first international planetary defense mission AIDA (Asteroid Impact and Deflection Assessment) in collaboration with the NASA DART (Double-Asteroid Redirection Test) mission [2], which was launched on 24 Nov 2021 and conducted a kinetic impact to Dimorphos on 26 September 2022. The purpose of the AIDA is to evaluate the asteroid deflection effect by the impact of spacecraft, which is now under investigation using the data observed by ground-based and space-borne observations. Detailed evaluation will be conducted by Hera, which will be launched in 2024 and rendezvous with the binary system in 2027 for the characterization of their surface physical properties, composition, geologic features, and dynamical motions, we well as the dimension of the crater formed by the kinetic impact of DART.
Hera Instruments: TIRI is one of the mission instruments onboard Hera, along with two asteroid flaming camera AFC, a laser altimeter PALT, a 25 color visible to near infrared imager HyperScout, and a 6U CubeSat Milani for spectroscopy and another 6U CubeSat Juventas for physical properties using a ground penetrating radar .
TIRI: TIRI consists of the sensor unit BOL and the electronics unit SHU, with the mass of 4.0 ± 0.4 kg, the power in operational mode of 17 ± 1 W, and the envelope size of 190 x 230 x 263 mm. Unregulated 28 V is supplied from the spacecraft for the activity and thermal control of TIRI. The telemetry and command communication will be conducted via SpaceWire. BOL is inherited from the UNFORM2 [3], while the logics of SHU are inherited from Hayabusa2 TIR and DE [4]. BOL is based on an uncooled bolometer (Lynred PICO1024 Gen2) of 1024 x 768 pixels. The observable wavelength range is at 8-14 µm for wide band, and 7-14 µm for six narrow bands. Its FOV is 13.3° x 10.0°, with the IFOV of 0.013°/pixel (0.23 mrad). Its detectable temperature ranges 150-400 K, and the NETD is estimated <0.1K at 300K.
TIRI Operations: TIRI will start observations after arrival at the Didymos binary system in 2027. In the Early Characterization Phase (ECP, 20-30 km from Didymos), TIRI will observe the entire binary system, taking one-rotation images of Didymos (2.26 hours) and one-revolution images of Dimorphos around Didymos (11.9 hours). Those images will be taken from the dawn, dusk, north-pole, and south-pole directions. During the Detailed Characterization phase (DCP, 8-20 km from Didymos), TIRI will observe Didymos and Dimorphos at higher spatial resolution for one-rotation of Didymos and one-revolution images of Dimorphs from the noon direction, in addition to the dawn, disk, north, and south directions. During the Close-up Operation Phase (COP, 4-22 km from Didymos), TIRI will observe the DART crater at a spatial resolution of < 1 m/pixel (from 4 km distance) during flyby. During the Extended Phase (EXP, close to 1 km from Didymos), TIRI will take consecutive thermal images of local areas of Didymos and Dimorphos, especially for the DART crater at the spatial resolution of <0.25 m/pixel. With these data, as well as the data from the other instruments, a progress in planetary science and also planetary defense will be expected in Hera mission.
References: [1] Michel P. et al. (2022) Planet. Sci. J., 3, 160, [2] Cheng A.F. et al. (2018) PSS 157, 104-115. [3] Fukuhara T. et al. (2017) IEEE Trans. Geosci. Rem. Sens. 55, 4314-4324. [4] Okada T. et al. (2017) Space Sci. rev. 208, 255-286.
Hera: Hera is the asteroid mission led by ESA [2] and a part of the first international planetary defense mission AIDA (Asteroid Impact and Deflection Assessment) in collaboration with the NASA DART (Double-Asteroid Redirection Test) mission [2], which was launched on 24 Nov 2021 and conducted a kinetic impact to Dimorphos on 26 September 2022. The purpose of the AIDA is to evaluate the asteroid deflection effect by the impact of spacecraft, which is now under investigation using the data observed by ground-based and space-borne observations. Detailed evaluation will be conducted by Hera, which will be launched in 2024 and rendezvous with the binary system in 2027 for the characterization of their surface physical properties, composition, geologic features, and dynamical motions, we well as the dimension of the crater formed by the kinetic impact of DART.
Hera Instruments: TIRI is one of the mission instruments onboard Hera, along with two asteroid flaming camera AFC, a laser altimeter PALT, a 25 color visible to near infrared imager HyperScout, and a 6U CubeSat Milani for spectroscopy and another 6U CubeSat Juventas for physical properties using a ground penetrating radar .
TIRI: TIRI consists of the sensor unit BOL and the electronics unit SHU, with the mass of 4.0 ± 0.4 kg, the power in operational mode of 17 ± 1 W, and the envelope size of 190 x 230 x 263 mm. Unregulated 28 V is supplied from the spacecraft for the activity and thermal control of TIRI. The telemetry and command communication will be conducted via SpaceWire. BOL is inherited from the UNFORM2 [3], while the logics of SHU are inherited from Hayabusa2 TIR and DE [4]. BOL is based on an uncooled bolometer (Lynred PICO1024 Gen2) of 1024 x 768 pixels. The observable wavelength range is at 8-14 µm for wide band, and 7-14 µm for six narrow bands. Its FOV is 13.3° x 10.0°, with the IFOV of 0.013°/pixel (0.23 mrad). Its detectable temperature ranges 150-400 K, and the NETD is estimated <0.1K at 300K.
TIRI Operations: TIRI will start observations after arrival at the Didymos binary system in 2027. In the Early Characterization Phase (ECP, 20-30 km from Didymos), TIRI will observe the entire binary system, taking one-rotation images of Didymos (2.26 hours) and one-revolution images of Dimorphos around Didymos (11.9 hours). Those images will be taken from the dawn, dusk, north-pole, and south-pole directions. During the Detailed Characterization phase (DCP, 8-20 km from Didymos), TIRI will observe Didymos and Dimorphos at higher spatial resolution for one-rotation of Didymos and one-revolution images of Dimorphs from the noon direction, in addition to the dawn, disk, north, and south directions. During the Close-up Operation Phase (COP, 4-22 km from Didymos), TIRI will observe the DART crater at a spatial resolution of < 1 m/pixel (from 4 km distance) during flyby. During the Extended Phase (EXP, close to 1 km from Didymos), TIRI will take consecutive thermal images of local areas of Didymos and Dimorphos, especially for the DART crater at the spatial resolution of <0.25 m/pixel. With these data, as well as the data from the other instruments, a progress in planetary science and also planetary defense will be expected in Hera mission.
References: [1] Michel P. et al. (2022) Planet. Sci. J., 3, 160, [2] Cheng A.F. et al. (2018) PSS 157, 104-115. [3] Fukuhara T. et al. (2017) IEEE Trans. Geosci. Rem. Sens. 55, 4314-4324. [4] Okada T. et al. (2017) Space Sci. rev. 208, 255-286.