Hi All I've used the launch timings to complete an analysis for a search orbit for Chang'e 5 after launch. The goal is to acquire it's TT&C radio beacon and further refine the orbit to maybe even allow suitably equipped observers to image it. I have noted over the years that China prefers to plan their lunar and deep space missions such that significant mission evens occur will the space craft is high over China as their deep space radio network is concentrated there. Using this knowledge greatly limits the possible cases of where Chang'e 5 will enter lunar orbit, thus allowing us to constrain a transfer orbit. Historically Chang'e 3 and 4 both used essentially direct trans-lunar injections well before the first orbit was completed. Interestingly LRO also used a similar method to get to the Moon. So looking at the coast times that these three missions took to get to the Moon revealed something interesting: LRO - 4.57986 days CE3 - 4.68261 days CE4 - 4.59861 days Earlier this week rumors abounded that CE5 will launch on November 24th. Using that knowledge I looked for the time the Moon would be overhead of the longitude of Beijing and found that was 2020-11-28T14:45:00 UTC. Looking back ~4.6 days revealed a launch window centered around 2020-11-24T00:00:00 UTC. https://twitter.com/coastal8049/status/1329197419616030720 Marco's observation of the NOTAM and a launch window centered on 2020-11-23T21:00:00 appears to agree with my guess that CE5 could arrive and the Moon for a LOI at approximately 2020-11-28T14:45:00 UTC. To create a search orbit, I then created two synthetic observations at the perigee (instantaneous TLI time) and at the guessed arrive at the moon for LOI. I then took the transfer orbit Bill Gray created for CE4 and I corrected with Doppler observations and fit those two points to it to correct the RAAN, MA, AoP and ECC. The orbit agrees reasonably well with where the Moon is at and the s/c in the parking orbit at the timings noted above. http://www.satobs.org/seesat/Dec-2018/0059.html CHANG'E 5 radio search orbit 1 70001U 20329.87500000 .00000000 00000-0 00000-0 0 07 2 70001 29.4496 17.0072 9572599 213.4938 32.8278 0.08563329 03 # 20201123.86-20201128.54, 2 measurements, 1.214 deg rms I've created a visualization of the orbit and it can be found here: https://twitter.com/coastal8049/status/1329565778966790146 Chang'e 5 will most likely emit on 2210.81 and/or 2257.68MHz. The ITU list these for the lander and orbiter respectively. CE4 and CE5T1 used 2210.81MHz. My guess is 2257.68MHz may be the TT&C for the returning sample return capsule. Regards, Scott Tilley ROBERTS CREEK 1: 8049 ST 49.4348 -123.6685 40. Scott Tilley ROBERTS CREEK 2: 8048 ST 49.4175 -123.6420 1. Scott Tilley Keep tabs on COSPAR 8049 on Twitter: https://twitter.com/coastal8049?lang=en On 2020-11-19 7:13 a.m., Marco Langbroek via Seesat-l wrote: > CHANG'E 5 parking orbit > 1 70000U 20999A 20328.83333333 .00000000 00000-0 00000-0 0 03 > 2 70000 023.5000 350.8367 0037296 133.1289 324.0771 15.81924308 00 _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Thu Nov 19 2020 - 18:16:58 UTC
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