ZDPS 2A & 2B

Spacecraft nº:

Chinese spacecraft nº: 254 & 255

Launch data: Designation  15049 (see table) Launch date  19 Sep 2015 - 23:01 UT Launch site  Taiyuan, LC-16 Launch vehicle  CZ-6 Mission  Technology ZDPS with deployed structure

ZDPS in launch configuration

Description:

• ZDPS-2 is a nano-satellite mission of thr Microsat Research Center, Zhejiang University, which performs an in-orbit test for formation flying technology with two identical nano-satellites, ZDPS-2A and ZDPS-2B.
• The main objectives of ZDPS-2 mission are as follows:
  • Demonstrate advanced guidance, navigation and control algorithms for formation flying.
  • In-orbit performance test of self-designed ammonia micro-propulsion system.
  • Validate the precision of the S-Band Inter-Satellite Pseudo-Noise(PN) code ranging system.
  • Validate the dual-frequency GPS receiver and the relative orbit determination algorithm.
  • Validate the MEMS accelerometer in-orbit calibration algorithm.
• Both ZDPS-2A and ZDPS-2B are 25 cm × 25 cm × 25 cm cube-shaped and weigh around 12 kg. The satellites are equipped with tri-junction Ga-As solar cells as the primary power, tiled on all six planes of the satellite body, which have a 26.8% theoretical efficiency, and a Li-ion battery pack of ten cells from Sanyo serves as the secondary power. The transceiver works under the Universal S-Band (USB) TTC system, with uplink data rates of 2 kbps and adjustable downlink data rates of 1 kbps to 64 kbps. The on-board computer( OBC) is composed of multi-CPU with FPGA, providing a universal computing, storage, management platform for command execution, TT&C, attitude and orbit control, payloads, etc. Sub-degree level attitude measurement will be achieved through a 3-axis magnetometer, a 3-axis MEMS gyroscope, four-quadrant analog sun sensors mounted on six surfaces and a digital sun sensor. Attitude control utilizes a momentum wheel, installed on the pitch axis, to provide both momentum bias and reaction actuation for pitch attitude maneuver, and three orthogonally mounted magnetic coils provide active control torque for detumbling and three-axis stabilization, with pointing accuracy of better than 2° and steady precision 0.1°/s. In order to obtain an accurate absolute position and velocity measurement, ZDPS-2 carries two GPS receivers. A UNICORE dual-frequency GPS receiver provides singlepoint positioning accuracy of 2 m (RMS), with observational data updating rate up to 10 Hz. A Zhejiang University developed GPS receiver provides absolute position accuracy of 2 m and velocity of 0.2 m/s. A dual-frequency GPS antenna is mounted on the zenith face. ZDPS-2A and B are each equipped with an S-Band inter-satellite communication transceiver to exchange position and velocity data, capable of providing data transmission rate of 8kbps and maximum communication range of 5 km. In addition, an S-Band PN code ranging system is designed to provide PN code rate of no more than 2Mcps, and ranging accuracy of 4 cm for 1Mcps code rate.
• Both satellites carried a deployable structure experiment, which was deployed in orbit.
• ZDPS-2A and B are both equipped with propulsion system, either of them can be treated as chief or deputy. The system uses liquid ammonia as a propellant with ISP greater than 900 Ns/kg. With the fuel mass of 0.318kg and the satellite mass of below 12kg, the system can provide a total ?V of 24 m/s.

Mission details:

• ZDPS 2A and 2B were launched in a cluster of 20 satellites on the maiden flight of the CZ-6 rocket.

External links:

• Satellite tracking:
  Real time satellite ZDPS 2A tracking Real time satellite ZDPS 2B tracking