China to launch lunar navigation and communication test satellites

HELSINKI – China is preparing to launch a pair of lunar test technology satellites for a planned suite of satellites to explore the moon.

The Tiandu-1 and Tiandu-2 satellites will be launched alongside Queqiao-2, a lunar communications relay satellite that will support the upcoming Chang'e Lunar Far Sight and South Pole missions.

Tiandu-1 and 2 will form and fly in lunar orbit and conduct tests for navigation and communication technology verification. Tests include satellite-to-ground laser ranging and intersatellite microwave ranging methods.

The purpose of the Tiandu satellites is to inform the design of China's proposed Queqiao lunar navigation and communications constellation. The system will provide support services for lunar surface operations. Robotic and crewed operations on the Moon, particularly at the Moon's south pole—an area of ​​intense interest—or the far side of the Moon have limits to line-of-sight communications.

Lunar constellations including positioning, navigation and timing services are also planned by Lockheed Martin and the European Space Agency. These systems will face challenges including connecting to ground stations on Earth and the lunar surface, integrating navigation and communications, maintaining links between satellites, and the harsh solar radiation environment.

However, early visions of China's Kyukyo constellation envisioned a vast spacecraft system stationed at ecospace and Earth-Moon Lagrange points, then expanding to form interplanetary stations.

The initial Tiandu tests are part of building infrastructure to support the China-led International Lunar Research Station (ILRS). That plan aims to establish a lunar base in the 2030s and DSEL is active in attracting international partners. China also plans to put a pair of astronauts on the moon before 2030.

Establishing lunar infrastructure will give its developer an opportunity to increase its space cooperation opportunities, soft power and space leadership.

Last year a senior Chinese space official called for plans to upgrade lunar infrastructure to be accelerated or lose a once-in-a-lifetime opportunity.

Lunar infrastructure, lunar payloads

China has begun developing its lunar infrastructure. The country already has an aging satellite orbiting the Earth-Moon Lagrange Point 2, tens of thousands of kilometers beyond the Moon. The 2018 mission supported the Chang'e-4 lunar lander and rover mission.

The new, larger Queqiao-2 mission will operate in a frozen, elliptical orbit to support the Chang'e-4, 6, 7 and 8 missions. Tiandu satellites will be the precursor to a larger system.

The 61-kg Tiandu-1 Ga dual-band integrated communications payload consists of a laser retroreflector, space router and other payloads. Tiandu-2 carries a communications payload of 15 kg.

Queqiao-2 and, separately, the Tiandu pair arrived in Wenchang in recent days. The multi-spacecraft Chang'e-6 probe was launched in early January. The latter will be launched on a Long March 5 rocket.

Chinese state media reported that the Queqiao-2 and Tiandu sats will be launched in the first half of the year. However, it will be launched in February or March by a Long March 8 rocket from the coastal Wenchang spacecraft. This will allow time to operate Queqiao-2 before the start of the Chang'e-6 lunar far-side return mission in May.