Spacecraft, communication method, and communication system

A communication method for communication between ground stations, the method comprising:

• transmitting, from a first ground station, data addressed to a second ground station so as to relay the data by inter-spacecraft communication;
• and
• relaying the data by the inter-spacecraft communication, wherein
• the inter-spacecraft communication includes
• transmitting the data, as an optical communication signal, from a first spacecraft to a second spacecraft,
• receiving, by the second spacecraft, the optical communication signal from the first spacecraft, and
• controlling an attitude by the second spacecraft,
• the second spacecraft includes
• an attitude control actuator configured to control an attitude of the second spacecraft,
• an imaging device configured to receive the optical communication signal from the first spacecraft, and
• an attitude controller configured to control the attitude control actuator, based on a position of the optical communication signal in an image obtained by the imaging device,
• wherein the imaging device is configured to be able to perform imaging at a first view angle, and imaging at a second view angle smaller than the first view angle, and
• the second spacecraft further includes a communication controller that switches the imaging device between a first mode of receiving the optical communication signal through the imaging at the first view angle, and a second mode of receiving the optical communication signal through the imaging at the second view angle, and
• controlling the attitude by the second spacecraft is performed by the attitude controller, based on the position of the optical communication signal in the image obtained by the imaging device.

A communication system for communication between ground stations, the system comprising:

• a first ground station;
• a second ground station configured to receive data transmitted from the first ground station;
• and
• a plurality of spacecraft used for relaying, by inter-spacecraft communication, transmission of the data from the first ground station to the second ground station, wherein
• the plurality of spacecraft include a first spacecraft that transmits the data as an optical communication signal, and a second spacecraft that receives the optical communication signal, and
• the second spacecraft includes
• an attitude control actuator configured to control an attitude of the second spacecraft,
• an imaging device configured to receive the optical communication signal from the first spacecraft, and
• an attitude controller configured to control the attitude control actuator, based on a position of the optical communication signal in an image obtained by the imaging device,
• wherein the imaging device is configured to be able to perform imaging at a first view angle, and imaging at a second view angle smaller than the first view angle, and
• the second spacecraft further includes a communication controller that switches the imaging device between a first mode of receiving the optical communication signal through the imaging at the first view angle, and a second mode of receiving the optical communication signal through the imaging at the second view angle.