We're coming up to the launch of #Tianwen1 tonight, the second #Mars mission launching this summer after @HopeMarsMission this past weekend.

Here's a tweet thread to get you primed for this ambitious mission! (1/n)

CNSA

#Tianwen1 is China's first *dedicated* attempt at #Mars, but not their first attempt!

In 2011, they flew Yinghuo-1, a tiny experimental spacecraft as a rideshare on the Russian Fobos-Grunt mission. (2/n)

NPO Lavochkin

Alas, Fobos-Grunt and Yinghuo-1 were not meant to be.

A propulsion error left the vehicle stranded in Earth orbit after launch, and it eventually re-entered and was destroyed.

China decided to do their own thing next. (3/n) https://www.nasaspaceflight.com/2012/01/fobus-grunt-ends-its-misery-via-re-entry/

#Tianwen1 is composed of two main parts, an orbiter (bottom) and a lander w/rover (top).

Combined, they are one of the largest payloads to go to Mars in a long time at over 5 tons (bigger than Curiosity or the Trace Gas Orbiter, even!) (4/n)

CASC

The #Tianwen1 orbiter is a hexagonal vehicle that will carry the rover along with it and scout landing sites when it arrives in February next year.

It's equipped with cameras, subsurface radar and a magnetometer, among other instruments. (5/n)

Jim Head

The #Tianwen1 lander will take the rover to the surface using some pretty conventional methods, including a heat shield, parachute, and descent propulsion.

It will leverage a lot of what they learned from Chang'e missions at the Moon. (6/n)

CNSA

The #Tianwen1 rover is slightly bigger than Spirit or Opportunity.

It carries with it a nice selection of instruments, including radar, cameras, and a ChemCam-like laser spectroscope. (7/n)

Sprt98

#Tianwen1 is launching on a Long Mach 5, China's heavy lift vehicle, which is now on the pad and ready to go.

It only successfully returned to flight in December, in the nick of time. Here's a video of the rollout. (8/n)

It's not looking like there is a #Tianwen1 livestream coming, but we'll keep an eye out just in case and retweet as necessary.

Our best guest is the launch will take place tonight, Wednesday 9:45pm PDT / 12:45am EDT (Thursday).

We did a full preview of #Tianwen1, plus the Hope probe which already launched and @NASAPersevere coming up next, in our Summer of Mars preview podcast. Listen in to get the full story! (10/10) http://www.wemartians.com/episode080