Besides the scientific merit (which is evident), what interests me most about the upcoming Chang'e 4 mission is their intention to get the public involved. With the previous Chang'e missions, there was some public interaction, mostly the posting of pictures taken by the probes or interacting with netizens through cutie social media accounts. But there will be more on Chang'e 4.
On January 8, 2016, the Chinese Lunar Exploration Program (CLEP) released an unusual "Call for Proposal" to the general public, for a small payload that may go on-board the Chang'e 4 lander and/or the planned relay satellite at Earth-Moon L2 point. The details of the call are available here (in Chinese). The payload is limited to 3 kilograms in mass and 20 watts of power. It seems CLEP is most interested in a payload that is useful for public outreach, although scientific merit and technical feasibility are also important. Proposals are due in late March. The winners will be announced some time in mid-2016. Unfortunately, the competition is only open to Chinese nationals (excluding personnel associated to the mission). CLEP notes that although "international contributions are welcome as usual", it is already considering proposals from international partners, therefore they are reserving this competition for Chinese nationals.
But this does not mean that you are hands-off everything from Chang'e if you are not a Chinese national. In fact, I am seeing China make effort to make robotic space mission information available to the public, but they are just not advertised much. Here are some resources I have collected over time that may be of interest to some.
1. Science Achievement Series of China's Lunar Exploration Program, which consists of three books at the moment (free e-books):
At the beginning of each book you will find a good amount of the information about Chang'e 1 and 2, from probe design, control system, to data reduction, etc. Hard copies are also available for purchase from Sino Maps Press (with a steep price tag -- $200 each).
2. Chang'e 2 zoomable map: (seems down at the moment; but alternative data access given below). The map was stitched from the 50m/pixel data from Chang'e 2.
These are a number of compressed files (TIFF or PDS format for Chang'e 1, PDS only for Chang'e 2) indexed by quadrangles. The PDS-format data (*.03 files) can be opened directly with NASAView. [And also with IMG2PNG. -ed.] The 50m/pixel Chang'e 2 data is used to construct the zoomable map described above.
4. Collections of processed/annotated images in JPG format: Chang'e 1, Chang'e 2, Chang'e 3 and Yutu. As these have been widely circulated already. You probably have already seen most of them.
[Note from the editor: If you have trouble with these instructions, have no fear; I will be posting some of the camera data from the Chang'e 3 mission in the future. --ESL]
China has its own Planetary Data System, maintained by the National Astronomical Observatories of China (NAOC). At the time of writing, most (all?) calibrated data (defined as "level 2" and "level 3") from Chang'e 1, 2 and 3 have been released (the raw data is still proprietary). The web interface does not have an English version, but it is not difficult to figure out how it works with some assistance from online translate tools. Note that the service may be unstable at times, especially for overseas users.
First, you need register an account. It is very easy! Just make sure to check your spam box for emails from NAOC (likely to be incorrectly encoded). Once you are logged in, you should be able to see all Chang'e 1, 2 and 3 products listed in the sidebar on the left (under a tag like "lunar exploration data release"). Note that there is another tag that might be incorrectly translated as "the whole month of web data download" -- it actually means "download global mosaic data" which we have already covered.
(In case you are wondering, the service agreement states that you can use the data as long as the purpose is for research or education and is non-commercial.)
You can choose any mission and there will be a webpage listing all the instruments. Find your favorite one, and look for "PDS" icon to the right. Click it. You will be redirected to a form for data selection. All the button labels are in Chinese, but there is a helpful page with text and graphic directions telling you which button to hit. The only thing that the help page does not cover is about the drop-down menus; there are three of them on the left and three on the right. The first (the upmost) one on the left is again the instrument; if you have previously choose which instrument you want to use, you don't need to alter this one; the second one is the level of the product, you need to choose either level 2 or level 3, or whatever is available. You probably don't need to alter other drop-down menus (the last one on the left is the sub-level of the product; the three on the right is the time window and result sorting).
After all, it is a bit like online shopping: you need to put interested items in the cart, and click "process order" before you can download them.
Have fun playing with the data. Ohh, this post wouldn't be completed without an image or two. Here is an image of the Tycho crater taken by the stereo CCD camera on-board Chang'e 2:
And, look at this! Yutu's footprint. Taken by the rover's PanCam on January 13, 2014, at 19:59:46 UT.