Navigation Technology

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Navigation Technology

Science in Space April 2025

Humans have always been explorers, venturing by land and sea into unknown and uncharted places on Earth and, more recently, in space. Early adventurers often navigated by the Sun and stars, creating maps that made it easier for others to follow. Today, travelers on Earth have sophisticated technology to guide them.

Navigation in space, including for missions to explore the Moon and Mars, remains more of a challenge. Research on the International Space Station is helping NASA scientists improve navigation tools and processes for crewed spacecraft and remotely controlled or autonomous robots to help people boldly venture farther into space, successfully explore there, and safely return home.

A current investigation, NAVCOM, uses the space station’s ISS Ham Radio program hardware to test software for a system that could shape future lunar navigation. The technology processes signals in the same way as global navigation satellite systems such as GPS, but while those rely on constellations of satellites, the NAVCOM radio equipment receives position and time information from ground stations and reference clocks.

The old made new

Sextant Navigation tested star-sighting from space using a hand-held sextant. These mechanical devices measure the angle between two objects, typically the Sun or other stars at night and the horizon. Sextants guided navigators on Earth for centuries and NASA’s Gemini and Apollo missions demonstrated that they were useful in space as well, meaning they could provide emergency backup navigation for lunar missions. Researchers report that with minimal training and practice, crew members of different skill levels produced quality sightings through a station window and measurements improved with more use. The investigation identified several techniques for improving sightings, including refocusing between readings and adjusting the sight to the center of the window.

Navigating by neutron stars

The station’s NICER instrument studies the nature and behavior of neutron stars, the densest objects in the universe. Some neutron stars, known as pulsars, emit beams of light that appear to pulse, sweeping across the sky as the stars rotate. Some of them pulse at rates as accurate as atomic clocks. As part of the NICER investigation, the Station Explorer for X-ray Timing and Navigation Technology or SEXTANT tested technology for using pulsars in GPS-like systems to navigate anywhere in the solar system. SEXTANT successfully completed a first in-space demonstration of this technology in 2017. In 2018, researchers reported that real-time, autonomous X-ray pulsar navigation is clearly feasible and they plan further experiments to fine tune and modify the technology.

Robot navigation

Crews on future space exploration missions need efficient and safe ways to handle cargo and to move and assemble structures on the surface of the Moon or Mars. Robots are promising tools for these functions but must be able to navigate their surroundings, whether autonomously or via remote control, often in proximity with other robots and within the confines of a spacecraft. Several investigations have focused on improving navigation by robotic helpers.

The SPHERES investigation tested autonomous rendezvous and docking maneuvers with three spherical free-flying robots on the station. Researchers reported development of an approach to control how the robots navigate around obstacles and along a designated path, which could support their use in the future for satellite servicing, vehicle assembly, and spacecraft formation flying.

The station later gained three cube-shaped robots known as Astrobees. The ReSWARM experiments used them to test coordination of multiple robots with each other, cargo, and their environment. Results provide a base set of planning and control tools for robotic navigation in close proximity and outline important considerations for the design of future autonomous free-flyers.

Researchers also used the Astrobees to show that models to predict the robots’ behavior could make it possible to maneuver one or two of them for carrying cargo. This finding suggests that robots can navigate around each other to perform tasks without a human present, which would increase their usefulness on future missions.

An investigation from ESA (European Space Agency), Surface Avatar evaluated orbit-to-ground remote control of multiple robots. Crew members successfully navigated a four-legged robot, Bert, through a simulated Mars environment. Robots with legs rather than wheels could explore uneven lunar and planetary surfaces that are inaccessible to wheeled rovers. The German Aerospace Center is developing Bert.

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Christian M. Getteau

Air Force Pilot, SkillBridge Fellow Helps NASA Research Soar

Jeremy Johnson laces his black, steel-toed boots and zips up his dark blue flight suit. Having just finished a pre-flight mission briefing with his team, the only thing on his mind is heading to the aircraft hangar and getting a plane in the air.

As he eases a small white-and-blue propeller aircraft down the hangar’s ramp and onto the runway, he hears five essential words crackle through his headset: “NASA 606, cleared for takeoff.”

This is a typical morning for Johnson, a research pilot and aviation safety officer at NASA’s Glenn Research Center in Cleveland. Johnson flies NASA planes to support important scientific research and testing, working with researchers to plan and carry out flights that will get them the data they need while ensuring safety.

Johnson hasn’t always flown in NASA planes. He comes to the agency from the U.S. Air Force, where he flew missions all over the world in C-17 cargo aircraft, piloted unmanned reconnaissance operations out of California, and trained young aviators in Oklahoma on the fundamentals of flying combat missions.

He’s at Glenn for a four-month Department of Defense SkillBridge fellowship. The program gives transitioning service members an opportunity to gain civilian work experience through training, apprenticeships, or internships during their last 180 days of service before separating from the military.

“I think SkillBridge has been an amazing tool to help me transition into what it’s like working somewhere that isn’t the military,” Johnson said. “In the Air Force, flying the mission was the mission. At NASA Glenn, the science—the research—is the mission.”

By flying aircraft outfitted with research hardware or carrying test equipment, Johnson has contributed to two vital projects at NASA so far. One is focused on testing how well laser systems can transmit signals for communication and navigation. The other, part of NASA’s research under Air Mobility Pathfinders, explores how 5G telecommunications infrastructure can help electric air taxis of the future be safely incorporated into the national airspace. This work, and the data that scientists can collect through flights, supports NASA’s research to advance technology and innovate for the benefit of all.

“It’s really exciting to see research hardware come fresh from the lab, and then be strapped onto an aircraft and taken into flight to see if it actually performs in a relevant environment,” Johnson said. “Every flight you do is more than just that flight—it’s one little part of a much bigger, much more ambitious project that’s going on. You remember, this is a small little piece of something that is maybe going to change the frontier of science, the frontier of discovery.”

Johnson has always had a passion for aviation. In college, he worked as a valet to pay for flying lessons. To hone his skills before Air Force training, one summer he flew across the country in a Cessna with his aunt, a commercial pilot. They flew down the Hudson River as they watched the skyscrapers of New York City whizz by and later to Kitty Hawk, North Carolina, where the Wright brothers made their historic first flight. Johnson even flew skydivers part-time while he was stationed in California.

Although he’s spent countless hours flying, he still takes the window seat on commercial flights whenever he can so he can look out the window and marvel at the world below.

Despite his successes, Johnson’s journey to becoming a pilot wasn’t always smooth. He recalls that as he was about to land after his first solo flight, violent crosswinds blew his plane off the runway and sent him bouncing into the grass. Though he eventually got back behind the stick for another flight, he said that in that moment he wondered whether he had the strength and skills to overcome his self-doubt.

“I don’t know anyone who flies for a living that had a completely easy path into it,” Johnson said. “To people who are thinking about getting into flying, just forge forward with it. Make people close doors on you, don’t close them on yourself, when it comes to flying or whatever you see yourself doing in the future. I just kept knocking on the door until there was a crack in it.”

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Hubble Visits Glittering Cluster, Capturing Its Ultraviolet Light

As part of ESA/Hubble’s 35th anniversary celebrations, the European Space Agency (ESA) shared new images that revisited stunning, previously released Hubble targets with the addition of the latest Hubble data and new processing techniques.

ESA/Hubble released new images of NGC 346, the Sombrero Galaxy, and the Eagle Nebula earlier in the month. Now they are revisiting the star cluster Messier 72 (M72).

M72 is a collection of stars, formally known as a globular cluster, located in the constellation Aquarius roughly 50,000 light-years from Earth. The intense gravitational attraction between the closely packed stars gives globular clusters their regular, spherical shape. There are roughly 150 known globular clusters associated with the Milky Way galaxy.

The striking variety in the color of the stars in this image of M72, particularly compared to the original image, results from the addition of ultraviolet observations to the previous visible-light data. The colors indicate groups of different types of stars. Here, blue stars are those that were originally more massive and have reached hotter temperatures after burning through much of their hydrogen fuel; the bright red objects are lower-mass stars that have become red giants. Studying these different groups help astronomers understand how globular clusters, and the galaxies they were born in, initially formed.

Pierre Méchain, a French astronomer and colleague of Charles Messier, discovered M72 in 1780. It was the first of five star clusters that Méchain would discover while assisting Messier. They recorded the cluster as the 72nd entry in Messier’s famous collection of astronomical objects. It is also one of the most remote clusters in the catalog.

Media Contact:

Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD

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NASA Tracks Snowmelt to Improve Water Management

As part of a science mission tracking one of Earth’s most precious resources – water – NASA’s C-20A aircraft conducted a series of seven research flights in March that can help researchers track the process and timeline as snow melts and transforms into a freshwater resource. The agency’s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) installed on the aircraft collected measurements of seasonal snow cover and estimate the freshwater contained in it.

“Seasonal snow is a critical resource for drinking water, power generation, supporting multi-billion dollar agricultural and recreation industries,” said Starr Ginn, C-20A project manager at NASA’s Armstrong Flight Research Center in Edwards, California.  “Consequently, understanding the distribution of seasonal snow storage and subsequent runoff is essential.”

The Dense UAVSAR Snow Time (DUST) mission mapped snow accumulation over the Sierra Nevada mountains in California and the Rocky Mountains in Idaho. Mission scientists can use these observations to estimate the amount of water stored in that snow.

“Until recently, defining the best method for accurately measuring snow water equivalent (SWE) – or how much and when fresh water is converted from snow – has been a challenge,” said Shadi Oveisgharan, principal investigator of DUST and scientist at NASA’s Jet Propulsion Laboratory in Southern California. “The UAVSAR has been shown to be a good instrument to retrieve SWE data.”

Recent research has shown that snow properties, weather patterns, and seasonal conditions in the American West have been shifting in recent decades. These changes have fundamentally altered previous expectations about snowpack monitoring and forecasts of snow runoff. The DUST mission aims to better track and understand those changes to develop more accurate estimates of snow-to-water conversions and their timelines.

“We are trying to find the optimum window during which to retrieve snow data,” Oveisgharan said. “This estimation will help us better estimate available fresh snow and manage our reservoirs better.”

The DUST mission achieved a new level of snow data accuracy, which is partly due to the specialized flight paths flown by the C-20A. The aircraft’s Platform Precision Autopilot (PPA) enables the team to fly very specific routes at exact altitudes, speeds, and angles so the UAVSAR can more precisely measure terrain changes.

“Imagine the rows made on grass by a lawn mower,” said Joe Piotrowski Jr., operations engineer for NASA Armstrong’s airborne science program. “The PPA system enables the C-20A to make those paths while measuring terrain changes down to the diameter of a centimeter.”

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NASA Marshall Fires Up Hybrid Rocket Motor to Prep for Moon Landings

NASA’s Artemis campaign will use human landing systems, provided by SpaceX and Blue Origin, to safely transport crew to and from the surface of the Moon, in preparation for future crewed missions to Mars. As the landers touch down and lift off from the Moon, rocket exhaust plumes will affect the top layer of lunar “soil,” called regolith, on the Moon. When the lander’s engines ignite to decelerate prior to touchdown, they could create craters and instability in the area under the lander and send regolith particles flying at high speeds in various directions.

To better understand the physics behind the interaction of exhaust from the commercial human landing systems and the Moon’s surface, engineers and scientists at NASA’s Marshall Space Flight Center in Huntsville, Alabama, recently test-fired a 14-inch hybrid rocket motor more than 30 times. The 3D-printed hybrid rocket motor, developed at Utah State University in Logan, Utah, ignites both solid fuel and a stream of gaseous oxygen to create a powerful stream of rocket exhaust.

“Artemis builds on what we learned from the Apollo missions to the Moon. NASA still has more to learn more about how the regolith and surface will be affected when a spacecraft much larger than the Apollo lunar excursion module lands, whether it’s on the Moon for Artemis or Mars for future missions,” said Manish Mehta, Human Landing System Plume & Aero Environments discipline lead engineer. “Firing a hybrid rocket motor into a simulated lunar regolith field in a vacuum chamber hasn’t been achieved in decades. NASA will be able to take the data from the test and scale it up to correspond to flight conditions to help us better understand the physics, and anchor our data models, and ultimately make landing on the Moon safer for Artemis astronauts.”

Fast Facts

• Over billions of years, asteroid and micrometeoroid impacts have ground up the surface of the Moon into fragments ranging from huge boulders to powder, called regolith.
• Regolith can be made of different minerals based on its location on the Moon. The varying mineral compositions mean regolith in certain locations could be denser and better able to support structures like landers.

Of the 30 test fires performed in NASA Marshall’s Component Development Area, 28 were conducted under vacuum conditions and two were conducted under ambient pressure. The testing at Marshall ensures the motor will reliably ignite during plume-surface interaction testing in the 60-ft. vacuum sphere at NASA’s Langley Research Center in Hampton, Virginia, later this year.

Once the testing at NASA Marshall is complete, the motor will be shipped to NASA Langley. Test teams at NASA Langley will fire the hybrid motor again but this time into simulated lunar regolith, called Black Point-1, in the 60-foot vacuum sphere. Firing the motor from various heights, engineers will measure the size and shape of craters the rocket exhaust creates as well as the speed and direction the simulated lunar regolith particles travel when the rocket motor exhaust hits them.

“We’re bringing back the capability to characterize the effects of rocket engines interacting with the lunar surface through ground testing in a large vacuum chamber — last done in this facility for the Apollo and Viking programs. The landers going to the Moon through Artemis are much larger and more powerful, so we need new data to understand the complex physics of landing and ascent,” said Ashley Korzun, principal investigator for the plume-surface interaction tests at NASA Langley. “We’ll use the hybrid motor in the second phase of testing to capture data with conditions closely simulating those from a real rocket engine. Our research will reduce risk to the crew, lander, payloads, and surface assets.”

Through the Artemis campaign, NASA will send astronauts to explore the Moon for scientific discovery, economic benefits, and to build the foundation for the first crewed missions to Mars – for the benefit of all.

For more information about Artemis, visit:

https://www.nasa.gov/artemis

News Media Contact

Corinne Beckinger 
Marshall Space Flight Center, Huntsville, Ala. 
256.544.0034  
corinne.m.beckinger@nasa.gov 

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Lee Mohon