[PPS03-P03] Flyby observation of Asteroid (3200) Phaethon by DESTINY+ onboard cameras
Keywords:Phaethon, DESTINY+, Flyby, Camera
In this mission, spatially resolved images of Phaethon will be taken by two onboard cameras, the Telescopic CAmera for Phaethon (TCAP) and the Multiband CAmera for Phaethon (MCAP) during the flyby, in order to understand the nature of a meteor shower's parent body, which is one of the sources of interplanetary dust particles that are thought to be an important transport medium of organic matter to the Earth. The spacecraft flybys Phaethon with a relative speed of 30 to 40 km/s. Despite such a high flyby speed, the cameras are required to take un-blurred images of Phaethon.
The main purposes of the DESTINY+ flyby observation of Phaethon is to understand the geology of a parent body of a meteor shower, and in particular constrain the dust ejection mechanisms from active (i.e., dust-ejecting) asteroids. The specific objectives of the camera observation are taking images for (1) obtaining the light curve of Phaethon in order to estimate the rotational period, (2) measuring the outline shape of Phaeton, (3) making a 3D shape model of Phaethon, (4) observing the surface geological features of Phaethon including dust ejection features, and (5) observing the surface material distribution of Phaethon. The observations (1) to (4) will be conducted by TCAP, and (5) by MCAP.
TCAP is a telescopic panchromatic camera for high spatial resolution imaging of the surface of Phaethon and have a rotational mirror for asteroid tracking during flyby. The rotational mirror can change the direction of the line of sight from 0 deg to 180 deg. This enables to observe Phaethon throughout the flyby with wide solar phase angles, which is extremely important to image and understand the surfaces of planetary bodies because the solar phase angle affects significantly the appearance of geological features in taken images.
MCAP is a multiband camera, the wavelengths of which are 400, 480, 550, 700, 850, and 950 nm (480 and 950 nm are optional bands) and has multiple optical systems and sensors in order to take all band images simultaneously. This is because there is not enough time to take each band image in turn with changing bandpass filters using such as a filter wheel in this high speed flyby mission. MCAP does not have a tracking mirror due to the weight limitation, and the line of sight of MCAP is fixed to the spacecraft with 40 deg off the relative velocity vector of the spacecraft.
We will explain the flyby imaging sequence of DESTINY+, and show the conceptual designs of TCAP and MCAP.