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New SIMPLEx Mission to Send SmallSats on Longest Deep Space Journey to Date

By Doug Messier
Parabolic Arc
September 15, 2020
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NASA rendering of a Janus satellite rendezvousing with a binary asteroid. (Credit: NASA)

BOULDER, Colo. (NASA PR) — A small satellite mission that will study the formation and evolutionary implications for small “rubble pile” asteroids has received NASA approval to proceed to the next phase of its development.

On Sept. 3, the dual-spacecraft Janus project successfully passed the important Key Decision Point-C milestone. It’s the first concept study from the current round of NASA’s Small Innovative Missions for Planetary Exploration (SIMPLEx-2) program to do so. 

Two other SIMPLEx-2 concepts, Escape and Plasma Acceleration and Dynamics Explorers (EscaPADE) and Lunar Trailblazer, are still in formulation. Lunar Trailblazer’s KDP-C is scheduled for this November, and EscaPADE’s is scheduled for April 2021.

Passing KDP-C means that the mission received agency-level approval for the Janus team to begin final design of hardware. The decision point also establishes the mission’s official schedule and budget. The mission will cost less than $55 million.

Janus’ twin spacecraft are designed to be small and agile, each one about the size of a carry-on suitcase. Shrinking the spacecraft brings an advantage, said Lockheed Martin’s Janus Program Manager Josh Wood. He explained that innovative technologies allow us to explore our solar system in new ways and address important science questions with smaller spacecraft. 

A binary asteroid is a system of two asteroids orbiting their common center of mass. Janus will meet up with two pairs of binary asteroids —designated 1996 FG3 and 1991 VH—each presenting differing orbital patterns. For instance, the pair called 1991 VH, has its own satellite, or “moon,” that whips around its larger “primary” asteroid following an erratic path. The 1996 FG3 pair, on the other hand, has a very stable orbital state. A suite of cameras on the Janus small satellites (SmallSats) will carefully track these dynamics with unmatched detail and build an accurate model of the two different binary asteroid systems.

“Binary asteroids are one class of objects for which we don’t have high-resolution scientific data,” said Daniel Scheeres, Janus Principal Investigator at the University of Colorado. “Everything we have on them is based on ground observations, which don’t give you as much detail as being up close.”

Janus will contribute to NASA’s goal of understanding our solar system’s content, origin and evolution. The mission also will inform planetary defense efforts and help fill in knowledge gaps as NASA moves forward with its plans for human exploration of the Moon and Mars.

“Janus will deliver big science in a small package,” said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at the agency’s Headquarters in Washington. “This SIMPLEx mission is the first such targeted science mission developed at reduced overall costs using new streamlined processes, while testing innovative technologies for use by future missions.”

Using small spacecraft — less than 400 pounds, or 180 kilograms in mass — SIMPLEx selections will conduct stand-alone planetary science missions. Each will share their ride to space with either another NASA mission or a commercial launch opportunity. 

After riding along with the launch of NASA’s Psyche mission in 2022, the Janus twins will first complete an orbit around the Sun, before heading back toward Earth for a gravity assisted sling-shot far into space and beyond the orbit of Mars.

The duo, named after the two-faced Roman god of beginnings and passages, will travel about four years to reach their destinations.

Janus is managed by the Planetary Missions Program Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama as part of the Solar System Exploration Program at NASA Headquarters in Washington. The program conducts space science investigations in the Planetary Science Division of NASA’s Science Mission Directorate at NASA Headquarters, guided by NASA’s agency priorities and the Decadal Survey process of the National Academy of Sciences. Janus is led by the University of Colorado Boulder, where the PI is based, which will also undertake the scientific analysis for the mission. Lockheed Martin will manage, build and operate the spacecraft.

For information on NASA’s small satellite activities, visit:

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