Queqiao: The Bridge Between Earth and the Far Side of the Moon
Science & Technology

Queqiao: The Bridge Between Earth and the Far Side of the Moon

The far aspect of the Moon all the time faces away from the Earth, making communications from lunar gear there rather more difficult. Happily, relay communication satellites can act as a bridge or stepping stone between transmission from the far aspect in direction of Earth floor stations. Credit score: House: Science & Expertise

Researchers clarify the design of the relay communication satellite tv for pc that enabled us to peek at the hidden face of the moon.

As a result of of a phenomenon known as gravitational locking, the Moon all the time faces the Earth from the similar aspect. This proved helpful in the early lunar touchdown missions in the twentieth century, as there was all the time a direct line of sight for uninterrupted radiocommunications between Earth floor stations and gear on the Moon. Nonetheless, gravitational locking makes exploring the hidden face of the moon–the far aspect–rather more difficult, as a result of indicators can’t be despatched instantly throughout the Moon in direction of Earth.

Nonetheless, in January 2019, China’s lunar probe Chang’e-4 marked the first time a spacecraft landed on the far aspect of the Moon. Each the lander and the lunar rover it carried have been gathering and sending again photos and information from beforehand unexplored areas. However how does Chang’e-4 probe talk with the Earth? The reply is Queqiao, a relay communications satellite tv for pc, explains Dr. Lihua Zhang from DFH Satellite tv for pc Co., Ltd., China.

As defined by Dr. Zhang in a evaluation paper just lately printed in House: Science & Expertise, Queqiao is an unprecedented satellite tv for pc designed particularly for one objective: to behave as a bridge between Chang’e-4 probe and the Earth. Queqiao was launched in 2018 and put into orbit round some extent ‘behind’ the Moon. This level is named the Earth-Moon Libration level 2, the place a particular case of gravitational stability permits Queqiao to take care of an orbit such that it has virtually fixed direct line of sight with each the far aspect of the Moon and the Earth. Getting the satellite tv for pc into this peculiar orbit required cautious planning and upkeep administration, and the success of this operation set a precedent for future makes an attempt at placing satellites in orbit round different Earth-Moon libration factors.

From its secure place in area, Queqiao helped information the soft-landing and floor operations of Chang’e-4 probe and has been our middleman with it ever since. The satellite tv for pc is supplied with two completely different varieties of antennas: a parabolic antenna and a number of spiral antennas. The former, which has a big diameter of 4.2 m, was designed to ship and obtain indicators on the X band (7-8GHz) to and from the rover and lander on the floor of the Moon. Its massive dimension is said the anticipated noise ranges and the low depth of the transmissions which can be despatched by floor gear.

On the different hand, the spiral antennas function on the S band (2-4 GHz) and talk with Earth floor stations, forwarding instructions to the lunar floor gear and exchanging telemetry and monitoring information. Most notably, all these completely different hyperlinks can transmit and obtain concurrently, making Queqiao extremely versatile. The evaluation paper addresses different essential design issues for Queqiao and future relay satellites, akin to the use of regenerative forwarding, the numerous hyperlink information charges concerned, and information storage programs for when no Earth floor station is accessible.

Over two years of exploration, a large amount of information has been obtained from the rover and lander by Queqiao. “Scientists in each China and different international locations have carried out evaluation and analysis based mostly on the retrieved information, and they’ve produced worthwhile scientific outcomes. The longer the operational life of Queqiao, the extra scientific outcomes can be achieved,” remarks Dr. Zhang. Based mostly on present predictions, Queqiao needs to be operable on mission orbit for at the very least 5 years.

Dr. Zhang additionally addressed the prospects for future lunar missions and how relay communication programs ought to evolve to assist them. Many unexplored areas on the Moon, akin to the largest crater at the South Pole, name for a number of relay satellites to take care of fixed communication hyperlinks, which poses an costly and time-consuming problem. However what if relay satellites have been appropriate for greater than a single mission?

“A sustainable communication and navigation infrastructure needs to be established to profit all lunar missions quite than coping with every mission independently,” feedback Dr. Zhang, “This infrastructure ought to undertake an open and extensible structure and present versatile, interoperable, cross-supportable, and appropriate communications companies, that are crucial to the success of future lunar explorations.” It’s probably that future endeavors on the far aspect of the Moon can be a take a look at on how properly we are able to cooperate to unveil the secrets and techniques of our pure satellite tv for pc.

Reference: “Improvement and Prospect of Chinese language Lunar Relay Communication Satellite tv for pc” by Lihua Zhang, 25 April 2021, House: Science & Expertise.
DOI: 10.34133/2021/3471608

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