Via the Lunar Listserv this morning I learned of the impending launch of a new lunar orbiter, Chang'E 2, planned for this Friday, October 1, from Xichang Satellite Launch Center in Sichuan. If I understand things correctly, most of the spacecraft is a duplicate of Chang'E 1 -- a "backup" spacecraft to the original, perhaps an engineering model -- though there are some key changes to instrumentation and to the mission operations plan. The most important change seems to be a lower orbit: Chang'E 1 operated in a 200-kilometer orbit, while Chang'E 2 will fly at only 100 kilometers, which has obvious implications for the quality and resolution of the science data.
Here are some other key differences between Chang'E 1 and Chang'E 2, as summarized by Qian Huang of the Shanghai Astronomical Observatory and Yong-Chun Zheng of the NAOC:
Chang'E 2 will have a shorter Earth to Moon cruise of 5 days rather than 12 days. The launch rocket has two more boosters to accomplish this more direct route to the Moon.
The laser altimeter's footprint will be smaller, and will achieve 5-meter vertical accuracy in estimate of the Moon's radius. It will also pulse more frequently, five times per second rather than just 1 time per second.
The main camera's spatial resolution will be 10 meters rather than 120 meters.
Late in the mission, the orbit will be lowered to an elliptical one with the same apolune (100 kilometers) but a perilune of only 15 kilometers!!
Tracking will be performed with new X-band radio capability.
Some things that will be the same as on Chang'E 1: Chang'E 2 carries the same imaging spectrometer, gamma/x-ray spectrometers, microwave detectors, and space environment monitoring system.
Zheng also remarked that "The mission goals of CE-2 will be focused into the high resolution image for the future landing site of CE-3 lunar lander and rover. The key technology about soft landing on the Moon will be tested in the CE-2 mission. The success of CE-2 will provide important technical basis for the successful implementation of China's future lunar exploration." There are unconfirmed rumors (not mentioned by either Zheng or Huang) that this spacecraft will deploy some sort of lander -- maybe a hard impactor or probe.
Japanese blogger Junya Terazono is collecting reports in Chinese and Japanese media about the impending launch. Here's the Google translation of his blog. He reports that the launch countdown process has already begun.