A tiny spacecraft built by two dozen undergraduate students at Tsinghua University is set to join the most heavily observed asteroid encounter in history: the April 2029 flyby of Apophis, a 340-meter near-Earth asteroid that will pass within 32,000 kilometers of Earth, closer than the ring of geostationary satellites.
The Student-led Threatening Asteroid Reconnaissance of Tsinghua (START) mission will fly past Apophis at a distance of just 7 kilometers during the moment of closest approach, capturing surface details at 8 centimeters per pixel. It is one of four missions from four space agencies and universities racing to reach the asteroid before and during its historic pass.
“This is a ‘doorstep’ deep space target,” said Bin Cheng, the mission’s chief scientist, presenting remotely from Beijing at the Apophis T-3 Years workshop in Padua, Italy, on June 19.
A rapid, low-cost approach
START was conceived in April 2025 and has moved at a pace that would make most space agencies envious. The spacecraft is a 200-kilogram class smallsat that will launch as a rideshare payload on a Landspace Zhuque-3 rocket in early 2028, provided at no cost by the Chinese launch provider.
Rather than embarking on a months-long interplanetary cruise, START will leverage Apophis’s close proximity to Earth. The spacecraft will first enter a roughly 1,000-kilometer parking orbit at 55 degrees inclination, then use its xenon solar electric propulsion system to raise the orbit to 31,600 kilometers over 200 days. From there, a short trajectory correction will put it on a collision course with Apophis at the precise moment of closest approach.
The approach removes the need for an interplanetary propulsion system, cutting both cost and mission complexity. At flyby, the spacecraft and asteroid will pass each other at a relative velocity of 8.74 kilometers per second, requiring fully autonomous tracking to keep the cameras locked on the target.
The total budget is approximately $2.8 million, funded through university support, donations, and corporate sponsorship (including the free launch, electric propulsion hardware, and camera components).
International fleet converging on Apophis
START will be the smallest and cheapest of four missions targeting the 2029 flyby, but its timing is carefully chosen. The student-built spacecraft is designed to capture the window of peak tidal stress, when Earth’s gravity will exert maximum force on the asteroid’s surface.
The other missions in the fleet are:
JAXA’s DESTINY+ spacecraft, originally launched to study asteroid Phaethon, has been retargeted to fly past Apophis in January 2029, serving as an early reconnaissance asset.
ESA’s Ramses mission will rendezvous with Apophis from February to August 2029, deploying two CubeSats (Farinella, an orbiter, and Don Quijote, a lander) for sustained observations. Ramses launches on an H3 rocket alongside DESTINY+ in April 2028 and builds on technology developed for ESA’s Hera planetary defense mission.
NASA’s OSIRIS-APEX, the former OSIRIS-REx spacecraft fresh from returning samples of asteroid Bennu, will rendezvous with Apophis in June 2029 for an 18-month observation campaign. The spacecraft will observe from approximately 50,000 kilometers during the closest approach before catching up to the asteroid. In a bold finale, it will fire its thrusters near the surface to expose subsurface material for spectroscopic analysis.
Science at the doorstep
Apophis’s 2029 flyby is a once-in-several-millennia event. An asteroid this large (roughly the size of three football fields) passes this close to Earth approximately once every 5,000 to 10,000 years. It will be visible to the naked eye for an estimated 2 billion people across Europe, Africa, and parts of Asia.
For planetary scientists, the flyby is a natural experiment. Earth’s gravity will alter Apophis’s spin, orbit, and potentially its surface structure, triggering landslides and “asteroid quakes” that will expose subsurface material without requiring a spacecraft to dig.
START’s dual visible-to-near-infrared hyperspectral imagers and its 8-centimeter-per-pixel resolution are designed to capture these changes in detail no other mission can match at the moment of peak stress. The larger missions provide sustained, multi-month observations; START provides the high-speed, high-resolution snapshot at the critical moment.
China’s growing planetary defense role
START is the latest in a series of Chinese planetary defense initiatives. China is planning an asteroid deflection test around 2027 using a separate impactor and observer spacecraft. Its Tianwen-2 sample return mission is currently approaching the near-Earth asteroid Kamo’oalewa and is expected to arrive in early July 2026.
The START team is already looking beyond Apophis. With its solar electric propulsion system, the spacecraft could be redirected to visit additional near-Earth asteroids after its primary mission, testing the limits of low-cost deep space exploration.
Cheng presented the mission at the Apophis T-3 Years workshop alongside representatives from NASA, ESA, and JAXA, a sign that even at a budget of $2.8 million, a student team can earn a seat at the table in humanity’s most ambitious asteroid observation campaign.