Speaker
Description
The close Earth approach of the Apophis is the first event in which 300 m size asteroid flybys with the altitude lower than GEO ring and the exciting event for mankind. The year 2029 in which the close flyby occurs is designated as “International Year of Asteroid Awareness and Planetary Defence” by the United Nation. Since the flyby occurs only 4 years later, the development of a new spacecraft for the Apophis observation is very challenging from the perspective of both of the cost and the development duration, the Japan Aerospace Exploration Agency (JAXA) is studying about the possibility of Apophis observation in space by using the JAXA operational satellites i.e. 12 satellites.
In this study, the observability from the perspective of visual magnitude, Earth shadow are evaluated in each satellite. The Apophis direction change rate, which affects the actual magnitude in the detector, is also taken into account to evaluate the observability. The JAXA 12 satellites are: 8 Sun-Synchronous Orbit (SSO), 2 Almost Circular Orbit (ACO), 1 High Elliptical Orbit (HEO), and 1 Geostationary Orbit (GEO). Some SSO satellites has long observable time i.e., 1.5 days in maximum because the Apophis direction from the satellite is almost the direction of the normal vector of the orbital plane. HEO satellite has good observability due to the characteristic of the orbit. GEO has the best observability which can observe Apophis all day. The visual magnitude decreases down to 3-4, which will be bright enough to detect by most of optical detector. The direction change rate in each satellite is under 0.025 deg/sec which is very slow and will not affect the actual visual magnitude by detectors.
Many of JAXA satellites has no optical mission component however there is still possibility to observe Apophis by on-board Star Tracker (STT). At the time of writing, we don’t have enough information what kind of detectors can be used for Apophis observation. We also have to consider about the attitude constraint, thermal constraint, power constraint and telecommunication ability of each satellite to determine whether we can observe Apophis by the satellite. We will proceed to confirm the information and study further on the possibility of Apophis observation by JAXA operational satellites.