2017 Mar 24
Friday, Day 83
Shenzhou 8 carried out a rendezvous and docking mission with Tiangong 1 (launched 2011 Sep 29 at 13:16 UTC). Soon after Tiangong was launched, China hinted that Shenzhou 8's launch was aimed to take place Nov 1 (Beijing time). The first firm indication of the actual launch date and time came from DLR, the German space organisation.
Based on Tiangong data from Oct 6 it was possible to calculate that if Shenzhou 8 were indeed to head for space on November 1 in the Beijing time zone, lift-off would occur October 31 at 21:50 UTC ±10 mins. For each day later, the time moves 28 minutes earlier. Conversely, for launch on an earlier date, it moves 28 minutes per day later.
When the date got nearer nearer and Tiangong had been settled in orbit for a few weeks, it was possible to look at the launch time again with a smaller degree of uncertainty. The results are shown in the table below.
Tiangong 1's orbit was following the pattern of earlier missions. It repeated its ground track every two days, leading to optimum launch opportunities occurring also every two days - Oct 31, Nov 2, Nov 4, etc..... The behaviour is an echo of Soviet rendezvous and docking operations with the Salyut/DOS space stations throughout the 1970s and the early-1980s, including the two-day approach phase after launch.
In the early hours of Oct 31, Chinese press sources confirmed the estimate of 21:58 UTC as the actual planned time of lift off. Shenzhou 8 launched at the first try so the alternate dates became academic but, for completeness, here are the dates and times from the zarya.info computation:
Oct 28, China issued the following Notice to Airmen covering the initial flight path of Shenzhou 8 across China. It affected the Lanzhou, Beijing, Shanghai and Wuhan air traffic control zones:
A1599/11 - A TEMPORARY RESTRICTED AREA ESTABLISHED BOUNDED BY N4204E10033-N4026E10006-N3435E11915-N3605E12012 BACK TO START. VERTICAL LIMITS: SFC-UNL.ALL ACFT ARE PROHIBITED TO FLY INTO THE AREA. SFC - UNL, 31 OCT 21:55 2011 UNTIL 31 OCT 22:30 2011. CREATED: 28 OCT 02:04 2011
A rough translation is that a temporary restricted zone is established within the box bounded by the co-ordinates given (the first one is 42° 04' north, 100° 33' east). It extends from the Earth's surface to unlimited altitude in flying terms - ie an upper limit of 15,000 metres (about 50,000 feet) or so, and all civil aircraft are prohibited from flying into the area. It is in effect October 31 between 21:55 and 22:30 GMT and it was published October 28 at 02:04 GMT.
Later in the day, a further NOTAM added a smaller area adjacent to the original one. It is not immediately obvious what it represented but a possibility was a no-fly zone in the operational area of one of the Yuanwang tracking ships stationed near the coast. In the event, the launch animation did not show a ship in that area, a little over 250 kilometres north of Shanghai:
On Oct 31, a further NOTAM superseded the original two and combined the areas:
At the same time as notifying the launch, Chinese authorities issued a NOTAM that covered a possible emergency landing should a problem arise with Shenzhou at launch. Retro-fire by Shenzhou during the first circuit of the Earth would have brough it down into the area defined by the NOTAM. It affected the Kunming air traffic zone:
Oct 31 - More NOTAMS
Oct 31 saw a new NOTAM for the emergency landing zone. It was a slight revision to the orginal, moving the probable touch-down point about 50 kilometres to the north-east. Given that the opening of the zone was unaltered from the previous version, it probably represented a change in the expected wind direction, with a greater south-westerly component.
On the map, the original zone is in grey and the revised one is in yellow. If used, Shenzhou would have travelled west-east (left to right) through it.
At the same time, a further no-fly zone was created in a strip of territory to the north-west of the emergency landing zone. It was off to one side of the ground track so it did not represent an area where debris of any kind would have landed. It may have been set up to ensure radar/radio 'silence' for equipment positioned to track an unplanned re-entry.
Copyright © Robert Christy, all rights reserved
Reproduction in whole or in part without permission is prohibited