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RFID Aids Space Exploration on Mars and Beyond

August 17th, 2018 Logistics - Features - Aerospace
By Claire Swedberg
NASA has deployed a fixed UHF RFID reading system known as REALM-1 on the International Space Station, while the REALM-2 flying RFID reading robot and REALM-3 Smart Stowage system are in the works for the coming years.

When scientists at the National Aeronautics and Space Administration (NASA) look toward deep space, with Mars exploration plans in place, they have some practical challenges ahead. One is the management of goodsequipment, tools and accessorieswith a limited crew or even no crew at all.

Part of the solution to asset management in space includes RFID technology. NASA's Johnson Space Center (JSC) has been leading an effort to design three solutions to identify tagged items in space, in order reduce the need for humans to manually search for items or confirm what they are, says Patrick W. Fink, the chief technologist for JSC's wireless and communication systems branch.

The technology is being tested on the International Space Station (ISS) in three of the craft's modules. The system includes NASA custom interrogators based on the Jadak ThingMagic M6e reader module, as well as antennas designed in-house by JSC engineers, transmitting data to NASA's own management software. To date, NASA reports, RFID use with the ISS (which began 18 months ago) has increased operational awareness of goods used in space.

The system, known as RFID Enabled Autonomous Logistics Management (REALM) for Exploration Missions, comes with three separate initiatives jointly funded by NASA's Advanced Exploration Systems (AES) and the ISS Programs. Those initiatives are REALMs 1, 2 and 3a fixed reader system designed to identify items moving from one part of the ship to another, a free-flying device with a built-in RFID reader to gain greater understanding of items' locations, and a smart storage cabinet that can read tagged items placed within its compartments.

NASA first began looking into RFID technology using handheld readers to supplement optical bar-code scanners in 2008. This served as a first step toward learning the effectiveness of RFID reads on spacecraft. But to be fully effective, the agency sought a hands-free solution that could provide zone-based location data without requiring a handheld reader.

The agency identified autonomous logistics management as a priority in 2015. It then began developing solutions, as well as looking at marketing the technologies to the commercial sector (see Johnson Space Center Seeks Partners to Market NASA-Developed RFID Technologies).

When it comes to space exploration, space stations require thousands of assets. Tracking these items requires the attention of highly skilled personnel, including crew members who could be using their time conducting laboratory research and operating the station. RFID offers a way to prevent lost items, and to make them faster to locate and retrieve when needed.

The ISS has about 118 cubic meters (4,167 cubic feet) of usable stowage space, and about 130,000 items that need to be tracked, with about 3,000 items currently missing. Lost items are a reality in the management of space stations. If something critical ends up missing, a "wanted poster" is created that includes the item's picture, part number or serial number, and last known location. On average, the crew then spends about 30 minutes before locating that item or a decision is made to relaunch a replacement. In deep-space missions, relaunching items is much more impractical or sometimes impossible.

There have been 13 wanted posters in 2018 to date, with missing items being requested due to having not been found during physical searches. Leading up to the REALM effort, approximately 3,200 items have been tagged so far, including cargo-transfer bags and some of the smaller items contained within.

In February 2017, the team first installed three sets of RFID readers on the ISS, which were delivered to the station aboard the HTV-6 Cargo Craft. Since that time, the RFID-based solution has located 100 missing items that had not been found during physical searches. As more items are tagged, researchers predict, the success rate is expected to increase.

JSC developed the RFID reader and antenna array, which consists of three reader clusters to track goods within the ISS modules, each with two readers attached to a total of eight antennastotaling six readers and 24 antennas. The readers can then be set for verbose mode, in which it transmits each tag transmission back to the Complex Event Processing (CEP) center on the ground, or event mode, with which the readers only send data back if conditions change. The read data is collected on an ISS laptop, which forwards that information to the CEP processing center.

The reader antennas required specialized design, Fink explains, since existing antennas with the desired performance were simply too large for the area inside the spacecraft. Thus, JSC designed its own reading unit, which comprises a multi-mode patch antenna.

"For polarization, readers tend to have circularly polarized antennas," Fink says. However, circularly polarized antennas typically lose tag response power by about 50 percent since tags are typically linearly polarized. Therefore, the team needed to build a system that could accomplish reliable reads of tags at any orientation, with a much smaller footprint than would be feasible with most reader antennas of the same performance level.

"What we did is build an antenna that changes polarization with frequency," Fink states, and that slowly rotates polarization across each of 52 channels using the frequency-hopping spread spectrum (FHSS) protocol. "With each one, the polarization is slightly different." The resulting antenna measures 5.5 inches square, with a comparable range to standard UHF RFID linear antennas. Two types of tags are used predominantly: Alien Technology's Squiggle on non-conductive items such as Styrofoam, and Metalcraft's Universal Mini on aluminum plates or other conductive items.

Since the system was launched in early 2017, with approximately 3,300 tagged items, there have been about 7.2 billion tags reads19 million reads per day, with about 1,500 unique tag reads daily. The readers compress data and forward it to the ground at 15-minute intervals, where JSC's software interprets and manages the data. When the technology is placed within a spacecraft destined for Mars, however, the software will reside in space so that data management can take place locally, before the filtered data is transmitted to Earth, Fink explains.

The software was updated in July of this year to enable automatic searches for missing items and automatic alerts based on the events, such as items that are not being detected by the readers or found in correct locations, via e-mails or text messages. The agency is also working on machine-learning capabilities to improve localization. By capturing and comparing information over time, Fink says, the system can understand "historically where this type of item is typically stored and what the RFID signatures look like for items in the specific storage location." That information, he notes, can enhance data regarding read events to help identify a given item's likely location as its tag is being read.

The next step will be REALM 2, a payload for a robotic free flyer known as the Astrobee, developed at NASA's Ames Research Center, that comes with a built-in RFID reader and antennas. This flying robot will be launched in April 2019 for use aboard the ISS. The flyer offers mobility and can go to areas that the fixed readers do not necessarily cover. The Astrobee measures 1 cubic foot, with cameras, sensors, a touch screen and UHF RFID read capability.

The Astrobee, which floats through the ISS reading tags as it goes, comes with an interrogator similar to that used by REAL-1, also based on the Jadak ThingMagic M6e reader module, with two antennas even smaller than the one used by REALM 1 readers, measuring 5 inches by 2.5 inches. Two additional antennas are textile-based and built into the skin of the robotic flyer, with the combined set of antennas facing four of Astrobee's six sides.

REALM-3 offers a smart stowage system to enable the real-time tracking of very dense collections of small items. NASA's JSC has already sent three smart stowage drawers into space, which have been capturing data for several years regarding which items are located in each drawer.

Patrick Fink
The REALM-3 system is being developed with deep space in mind. Readers are attached to fabric antennas built into a stowage structure that consists of drawers or shelves in which small items are stored. In that way, ISS crews or robots know exactly what items are inside each drawer, so that they can be quickly accessed as needed. Ground crews, in the meantime, have an up-to-date inventory count, which means items (a package of batteries, for instance) can be replenished before they are at risk of running out.

By 2020, NASA intends to have all three REALM projects completed, with the technology in use aboard the ISS. Additionally, the agency has deep-space plans for a habitable spacecraft, with an anticipated 2023 launch.

In the future, Fink says, other technologies may be evaluated as well. For instance, NASA's Small Business Innovation Research (SBIR) program uses optical sensor technology in conjunction with RFID to provide a more granular location for each tagged item. "We see that in our long-term road map," he says, since more specific location data could help the system to identify the exact rack on which an item may be located. It could also be used by robots aboard unmanned spacecrafts, by providing highly accurate location data for the robots that might be undertaking tasks such as unpacking cargo or replacing a part.