Tianwen-1 At Mars Options

[Huguet]

New Photos from medium-res camera. Detail of mars tiny limb.

https://mobile.twitter.com/AJ_FI/status/1375401463682306051

Attached thumbnail(s)

 

[kymani76]

Map of Tianwen-1 landing site in Utopia Planitia based on coordinates published in an article by Andrew Jones.
Landing ellipse is 100x40 km, ellipse azimuth orientation estimated from orbiter's orbital inclination of 87.7 degrees.

[kymani76]

A close-up of the central area.

Once the mapping thread for the mission is established the maps can be moved there.

[Phil Stooke]

Very nice maps! Once we are safely down I will start a map thread and these can be the first posts.
Phil

[Art Martin]

A close-up of the central area.

Once the mapping thread for the mission is established the maps can be moved there.

Wow, that's a gutsy first landing given how tough it is just to set down safely on a Martian surface with almost no obstacles and they are aiming for a spot adjacent to a rather scary looking crater. Wouldn't take much during that 7 minutes or so of "terror" timing to be off by a significant amount. I wonder how much hover and maneuver time they have built into the lander to be able to spot and avoid large obstacles at the last minute.

[Antdoghalo]

There are also a lot of pseudocones and lava wrinkles/channels in the landing ellipse too.

[john_s]

Given the size of the landing ellipse, there's very little chance of landing next to that crater right in the center of the ellipse. I suspect it's just coincidence that the ellipse center is on the rim of that crater.

John

[djellison]

Yeah - the landing ellipse is almost certainly larger than that entire image.

[kymani76]

I guess there are many uncertainties, but this map is a start, based on limited data available.
Landing ellipse could certainly be bigger, I got 100x40 km from Twitter source, so far from 100% reliable. Couldn't find this information
in any Chinese source to confirm it's really true. The landing coordinates precision (24,748N, 110,318E) by itself carries about 100 meters imprecision in any direction.
CTX camera images are also not absolutely referenced, although I did check different images to confirm that the coordinates really work out to be at crater's rim.

On the other hand the two high resolution images published so far do show area at the center of the map, so they could be working towards landing near the center of the ellipse.

And thank you Phil. It is always nice to get encouraged by the best.

[kenny]

Apollo 12 in 1969 was trying to land close to the dead Surveyor 3 craft, which was located inside a sizeable lunar crater with internal slopes which could not be landed on safely. So the Commander asked the navigation team to target him directly at Surveyor, on the basis that, due to landing errors, this was the best way to AVOID hitting Surveyor or descending inside its crater! The same rationale might apply here -- aim for the place that you least want to arrive at, in the sure knowledge that actually getting there is extremely unlikely!

[kenny]

Apollo 12 in 1969 was trying to land close to the dead Surveyor 3 craft, which was located inside a sizeable crater with internal slopes which could not be landed on safely. So the commander asked the navigation team to targeted him directly at Surveyor, on the basis that, due to landing errors, this was the best way to AVOID hitting Surveyor or decending inside its crater! The same rationale might apply here -- aim for the place that you least want to arrive at, in the sure knowledge that actually getting there is extremely ulikely!

[tdemko]

Apollo 12 in 1969 was trying to land close to the dead Surveyor 3 craft, which was located inside a sizeable crater with internal slopes which could not be landed on safely. So the commander asked the navigation team to targeted him directly at Surveyor, on the basis that, due to landing errors, this was the best way to AVOID hitting Surveyor or decending inside its crater! The same rationale might apply here -- aim for the place that you least want to arrive at, in the sure knowledge that actually getting there is extremely ulikely!

This phenomena played a role in the plot of the novel Gravity’s Rainbow by Thomas Pynchon, wherein the German V-2 engineers would observe the impacts of ballistic rocket tests from the center of the targeted bullseye.

[Huguet]

We are entering the week distance window of the estimated landing date (17/may), from 10/may till 24/may.

As expected no info, but if they continue with the estimated dates, soon they will try the landing.

https://www.uol.com.br/splash/noticias/afp/...-afp-7-dias.htm
AFP international news for 7 days, land probably before May 15.

"China's Tianwen-1 mission getting set to try and land Zhurong rover on Mars"
https://www.abc.net.au/news/science/2021-05...nding/100101552

[tolis]

I don't think the entry module will be "detaching from an orbiter 70 kilometres above the surface", that's already in the atmosphere!
Instead it would be detaching from the orbiter somewhere along the orbit, the question is then how to change the entry module orbit to
intersect the atmosphere. For Viking, the entry module carried its own propulsion system for this purpose.

[Huguet]

Indeed not less than 200km at periapsis. Timing for Zhurong to start its landing maneuver, in UTC, by Edgar Kaiser, based on the orbiter periapsis and time over the landing guessed coordinates on Utopia Planitia:

Mars in sight over China
2021.05.10 20:33:02 SKIPPED
2021.05.12 21:47:53 SKIPPED
Mars off sight over China
2021.05.14 23:02:44 DATE OF LANDING, BY SOURCE QUOTING CAST (by Cosmic_Penguin)
2021.05.17 00:17:35
2021.05.19 01:32:26
Mars in sight over China
2021.05.21 02:47:17 In sight with Jiamusi Antenna: https://en.wikipedia.org/wiki/Chinese_Deep_Space_Network
2021.05.23 04:02:08
2021.05.25 05:16:59
Last periapsis on May:
27/05/2021 06:31
29/05/2021 07:46

Date of Landing, by a source quoting CAST:
https://twitter.com/Cosmic_Penguin/status/1...701561030123521

More from Edgar Kaiser, that sugests we could have an atempt at today window: "Tianwen-1 showed quite some ground station activity along yesterday's approach to apoapsis. Tonight, at 21:47:53 UTC it will pass periapsis again."
Based on Mars position in the sky on the periapsis dates, chinese would have best comunication with the Tianwe-1 only today, bad sight on 14, 17 and 19th, so it apears that today could be the last window till may 21th.
https://twitter.com/df2mz/status/1392384013986410504

Orbital Period is 49h 14m 51s
https://twitter.com/df2mz/status/1391876766294331395

Good Thread following the landing from kaynouky
https://twitter.com/Kaynouky/status/1392051005664239619