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2022 May 19
Thursday, Day 139

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Does Yuan Wang 5 Sailing Plan Reveal Chang'e 3 Launch Date?

When a CZ-4C rocket took of from Taiyuan carrying three satellites, the complex operation to release them from the launch vehicle was due to take place well away from Chinese territory so it needed the services of one of China's Satellite Maritime Tracking and Control Department's fleet of ocean-going tracking stations to ensure all went well. Yuan Wang 5 was despatched to the Indian Ocean to oversee the event.

Early Tasks

Yuan Wang 5 left its base on the Yangtse river on May 30, and headed out onto the Pacific Ocean to support the Shenzhou 10 mission due for launch on June 11. It joined Yuan Wang 3 and Yuan Wang 6, the only other two active ships in the fleet. They set off about six weeks earlier - initially to support the Chinasat 11 geosynchronous launch on May 1 and then to wait for the Shenzhou 10 lift off on June 11.

Between missions, Yuan Wang 6 called in at Auckland, New Zealand and Yuan Wang 3 stopped by at Suva, Fiji.

Disposition of the three ships in a line across the Pacific Ocean on June 25 can be seen on a map describing how they were involved in Shenzhou 10's return to Earth.

After Shenzhou re-entered, all three ships got under way and pointed their bows towards China. Yuan Wang 3 and Yuan Wang 6 had sailing plans aimed to put them back in port late morning (UTC) on July 6. Yuang Wang 5 turned towards the south and was obviously not going home.

On July 4, Yuan Wang 5 arrived in Jakarta Bay, Indonesia. After a few hours at anchor, it entered port to replenish supplies, undertake necessary repairs and give its crew some shore leave. Plans filed with the port authority showed it as due to depart after seven days It departed July 11, heading for the Indian Ocean to support a three-satellite launch from Taiyuan to sun-synchronous orbit on July 19.

While it was there, it monitored launch of Shijian 11-05 from Jiuquan on July 15 although, had the July 19 launch not been on the cards, a specific trip for this mission would not have been scheduled.

End of Voyage

A sailing plan, listed on numerous shipping websites, indicated Yuan Wang 5 as not being due back on the Yangtse until December 4 at 05:00 UTC. It does not exclude the ship from returning to China but indicates that it is scheduled to remain operational and undertake a number of tracking tasks until then.

The Yuan Wang 3 and Yuan Wang 6 sailing plans allowed about ten and a half days between being released from Shenzhou/Tiangong duties and arrival at port. Assuming Yuan Wang 5 will take a similar length of time to sail back to China in December, we have an indication of when the active part of its tour of duty is due to end. Ten and a half days before the planned arrival home is November 23.

Relevance to Chang'e 3

For the Chang'e 2 launch, all three ships were deployed mid-Pacific. Chang'e 3 will depart Xichang along a similar ground track to its predecessor so it will have a similar downrange tracking requirement.

Chang'e 2 launch trajectory

For Yuan Wang 5 to be back in port early-December, launch of the Moon lander has to have occured before then.

If Chang'e 3 uses a similar launch window to its predecessors, there is an opportunity in the period between November 21 and November 23. A zarya.info web page describes how the date arises.

It begs the question of whether, by filing this particular sailing plan for Yuan Wang 5, China has inadvertently flagged-up November 21-23 as its chosen window for launch of Chang'e 3.

Page Date: 2013 July 23
(Created from Zarya Blog entry, 2013 July 7)

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