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Rendezvous

Match Orientation

Match Speed

Align

WHAT THE SERVICER MUST DO

Identify

Client

Servicer

Computer 

processes 

data and 

sends 

commands

Servicer’s 

sensors 

track the 

client

I

magine one spacecraft chasing another 

satellite and steadily closing the gap – 

with each vehicle traveling more 

than 16,000 miles per hour in the 

darkness of space.

The satellite that’s being 

chased, the client, is a 

multi-ton craft that is 

running out of fuel.

The chaser satellite, 

the fully robotic 

Restore-L servicer, 

follows in hot pursuit, 

carrying life-saving 

propellant and 

tools. It is steadily 

controlled by humans 

on the ground – 

for now.

Everything hinges on 

the servicer’s ability 

to accurately locate, 

catch up to, and 

match its speed with 

the client satellite.

But such a rendezvous 

isn’t easy. 

The client was not designed 

to be serviced. It does not have 

any markings that would make it 

easy for the servicer to find it and 

track it. The servicer has to do this on 

its own, using a machine vision system.

To make the matter more 

complex, Restore-L is far 

from Earth. There’s a delay 

getting data down to Earth – and 

commands back up to space. 

Humans on the ground cannot 

command the servicer 

quickly and accurately 

enough in the last few 

feet of the rendezvous to 

prevent a crash.

This means that 

Restore-L not only 

needs to perform 

relative navigation 

with its client – it 

needs to do it 

autonomously (by 

itself, with no human 

guidance) – and 

in real time, as the 

scenario unfolds.

NASA is developing this 

type of ground-breaking 

relative navigation system 

– not just for Restore-L, but 

for missions for decades to 

come, including the 

Journey to Mars.

Key parts of the system are being 

proven on the International Space Station 

through a test bed called Raven.

National Aeronautics and 

Space Administration

Creating Autopilot for Spacecraft

And How Raven Helps

How does Raven work?

How will it help other NASA missions?
Left image: the Raven 

module, prelaunch.

Top image: Artist’s 

representation of Raven 

tracking a vehicle 

approaching the International 

Space Station.

National Aeronautics and Space Administration

Goddard Space Flight Center

8800 Greenbelt Road

Greenbelt, MD 20771

www.nasa.gov

Raven

Helping NASA test 

autopilot technologies

What is Raven? Raven is a technology-filled 

module on the International Space Station 

that will help NASA test key elements of a new 

spacecraft autopilot system. Through Raven, 

NASA will be one step closer to having a relative 

navigation capability that it can take “off the 

shelf” and use with minimum modifications for 

many missions – for decades to come.

What’s in the box? Within its silver frame, Raven 

contains a carefully curated system that includes:

• Sensors: visible, infrared, and lidar

• A high-speed processor, and

• Advanced algorithms.

How it works. As spacecraft approach the 

International Space Station, Raven’s components 

join forces to independently image and 

track them.

• First, Raven’s sensors feed the data they 

“see” to a processor, which runs special pose 

algorithms to gauge the relative distance 

between Raven and the spacecraft it 

is tracking. 

• Then – based on these calculations – the 

processor autonomously sends commands 

that swivel the Raven module on its gimbal to 

keep the sensors trained on the vehicle – and 

continue tracking it.

• While these maneuvers are taking place, 

NASA operators on the ground are 

evaluating how Raven’s technologies are 

working together as a system, and making 

adjustments to increase Raven’s 

tracking performance.

How does Raven help NASA? Raven tests 

foundational technologies that will help NASA 

for decades to come. The Restore-L servicing 

mission will draw on its technologies when its 

robotic servicer navigates to Landsat 7 to refuel 

it in orbit. Other NASA missions could also draw 

on Raven technologies when rendezvousing. 

Who developed it? Raven was developed and 

integrated by the Satellite Servicing Projects 

Division (SSPD) at NASA’s Goddard Space Flight 

Center. SSPD will operate Raven during its twoyear lifespan.

When did it launch? Raven launched 

to the space station in 2017 aboard the 

Space Test Program-Houston 5 (STP-H5), a 

complement of 13 unique experiments from 

seven different agencies.