Queqiao: The bridge between Earth and the far side of the moon

Queqiao: The bridge between Earth and the far side of the moon
The far facet of the Moon at all times faces away from the Earth, making communications from lunar gear there way more difficult. Happily, relay communication satellites can act as a bridge or stepping stone between transmission from the far facet in direction of Earth floor stations. Credit score: Area: Science & Know-how

China’s Chang’e-Four probe marked the primary soft-landing of a spacecraft on the far facet of the Moon, which at all times faces away from Earth. To speak with floor stations, Chang’e-Four depends on Queqiao, a relay communication satellite tv for pc that orbits some extent behind the Moon and bridges Earth and Chang’e-4. In a evaluate, researchers clarify the design of Queqiao and depict the way forward for lunar relay communication methods.

Due to a phenomenon known as gravitational locking, the Moon at all times faces the Earth from the identical facet. This proved helpful within the early lunar missions within the 20th century, as there was at all times a direct line of sight for uninterrupted radiocommunications between Earth floor stations and gear on the Moon. Nevertheless, gravitational locking makes exploring the hidden face of the moon—the far facet—way more difficult, as a result of alerts can’t be despatched instantly throughout the Moon in direction of Earth.

Nonetheless, in January 2019, China’s lunar probe Chang’e-Four marked the primary a spacecraft landed on the far facet of the Moon. Each the lander and the lunar rover it carried have been gathering and sending again photographs and from beforehand unexplored areas. However how does Chang’e-Four 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 evaluate paper not too long ago printed in Area: Science & Know-how, Queqiao is an unprecedented satellite tv for pc designed particularly for one objective: To behave as a bridge between Chang’e-Four 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 of gravitational steadiness permits Queqiao to take care of an orbit such that it has virtually fixed direct line of sight with each the far facet 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 steady place in area, Queqiao helped information the soft-landing and floor operations of the Chang’e-Four probe and has been our middleman with it ever since. The satellite tv for pc is supplied with two totally different sorts of antennas: A parabolic antenna and several other spiral antennas. The previous, which has a big diameter of 4.2 m, was designed to ship and obtain alerts on the X band (7-8GHz) to and from the rover and lander on the floor of the Moon. Its massive dimension is expounded to the anticipated noise ranges and the low depth of the transmissions which can be despatched by floor gear.

However, the spiral antennas function on the S band (2-Four GHz) and talk with Earth floor stations, forwarding instructions to the lunar floor gear and exchanging telemetry and monitoring knowledge. Most notably, all these totally different hyperlinks can transmit and obtain concurrently, making Queqiao extremely versatile. The evaluate paper addresses different essential design issues for Queqiao and future relay satellites, reminiscent of using regenerative forwarding, the assorted hyperlink knowledge charges concerned, and knowledge storage methods 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 way of Queqiao. “Scientists in each China and different international locations have performed evaluation and analysis primarily based on the retrieved knowledge, they usually have produced useful scientific outcomes. The longer the operational lifetime of Queqiao, the extra scientific outcomes will likely be achieved,” remarks Dr. Zhang. Primarily based on present predictions, Queqiao needs to be operable on mission orbit for not less than 5 years.

Dr. Zhang additionally addressed the prospects for future lunar missions and the way relay communication methods ought to evolve to assist them. Many unexplored areas on the Moon, reminiscent of the most important crater on 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 had been appropriate for greater than a mission? “A sustainable communication and navigation infrastructure needs to be established to profit all lunar missions fairly than coping with every mission independently,” feedback Dr. Zhang. “This infrastructure ought to undertake an open and extensible structure and supply versatile, interoperable, cross-supportable, and suitable communications providers, that are essential to the success of future lunar explorations.” It is probably that future endeavors on the far facet of the Moon will likely be a take a look at of how nicely we are able to cooperate to unveil the secrets and techniques of our pure satellite tv for pc.

China satellite tv for pc heralds first mission to far facet of Moon

Extra info:
Lihua Zhang, Growth and Prospect of Chinese language Lunar Relay Communication Satellite tv for pc, Area: Science & Know-how (2021). DOI: 10.34133/2021/3471608

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Queqiao: The bridge between Earth and the far facet of the moon (2021, June 11)
retrieved 11 June 2021
from https://phys.org/information/2021-06-queqiao-bridge-earth-side-moon.html

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