Apr 01, 2014After more than five years investigating the development of a passive ultrahigh-frequency (UHF) RFID system for tracking assets and equipment for spaceflight applications, including on the International Space Station (ISS) and for future deep space missions, the National Aeronautics and Space Administration (NASA)'s Johnson Space Center (JSC) is seeking partners to market the technologies for use in the commercial sector as well, and to collaborate with NASA to further develop solutions.
NASA has developed a variety of RFID-based products, including RFID-enabled cabinets to track tagged items stored within them, and a system utilizing RFID sensors to make sure that proper torque is applied to a bolt or other fastener. The technologies are at various readiness levels, according to Patrick W. Fink, JSC's chief technologist for the wireless and communication systems branch, depending on the specific application.
The asset-tracking system deployed on the ISS helps NASA track the locations of approximately 20,000 items via bar-code and RFID technologies. Staff members are employing bar-code scanners to update information data in the agency's software, while NASA has used handheld RFID readers to evaluate how it can expedite audits, and to help locate missing items. An initial smart cabinet has been launched to allow on-demand audits of internal contents from the ground, Fink adds. In addition, NASA engineers are currently evaluating architectures with RFID readers installed at the hatches between different ISS modules.
While tracking small items on a large space station may already be challenging, doing so without gravity is even more difficult. At zero gravity, the assets must all be containerized and the containers must be strapped to walls. If a container is opened, the items within could potentially float away and become lodged somewhere, and then be overlooked for days or weeks. As a result, NASA is using RFID to manage those assets, while developing other solutions to expand the technology's effectiveness.
The International Space Station supports missions in space with crew shifts that may last for about six months, during which a half-dozen crewmembers spend that time conducting laboratory research and operating the station. To ensure that medicines, tools and personal belongings (such as clothing) can be accounted for, personnel historically have used bar codes, both on the ground and in space, to locate items and ensure they are ready for use by the crew. However, Fink says, the bar-code scanning process was time-consuming enough that inventory audits could not be conducted as often as originally intended.
By the early 2000s, Fink says, JSC began looking into RFID technology to help track assets and consumables, including medical supplies, amounting to about 20,000 items. "The space station is a living laboratory and the crew are periodically changing," he states, making it that much more difficult to monitor the locations of onboard assets.
In 2007, JSC began looking into the use of passive RFID tags utilizing surface acoustic wave (SAW) technology to help it take inventory of consumable items in space (see NASA to Launch RFID Test to Track Crewmember Supplies), which initially showed promise for use on the space station, Fink says. However, NASA carried out similar tests with EPC Gen 2 UHF tags (see NASA, Intermec Partner to Send RFID Into Space), and discovered that these new tags out-performed the SAW labels in terms of reliability and the ability to read individual tags within larger populations. Therefore, in 2008, JSC began experimenting with placing the new Gen 2 tags on items that would go into space aboard the station. However, JSC still intends to employ SAW technology for some sensor-based tracking related to temperature, pressure or other condition measurements in very extreme environments.
JSC is investigating RFID as part of what it calls the Autonomous Logistics Management (ALM) concept, which is focused on three themes: dense zone identification of items inside an RF-shielded enclosure or "smart drawer" (such as small goods packed tightly together); sparse zone identification of items located in open areas, including anything that may be packed in a bag, or that may have been inadvertently released from such a container and floated to an unknown location aboard the space station; and software for receiving RFID data and inferring the location of some items, based on the context of their reads.
As an example of the third theme, if the tag attached to a cargo transfer bag (CTB) is interrogated at a specific location, even if some of the tags of items stored within that bag are not read, the software infers that those objects are located there as well. Most tagged items are, in fact, located in CTBs, considered sparse reading areas. As many as 75 items can be stored in a single bag, many of them tagged, and JSC software, in turn, stores data indicating the tag to which each item is linked. By using a UHF RFID handheld reader, the station's crew can interrogate tags inside the bag without having to open it. This is important, because there is a risk, every time a bag is opened, that goods may float away. To inventory the bags' contents via a bar-code scanner, Fink says, took 20 to 30 minutes, since each bag had to be resealed every time an item was removed and scanned. With RFID, the inventory process takes about 20 seconds to complete.
NASA is also investigating the use of fixed portal readers that can be installed at specific locations, Fink says, such as chokepoints between one area of the station and another. In that case, if a bag were carried through the portal, the software would be updated to indicate the new zone in which that bag and its contents could be found.
If crewmembers are searching for a missing item, they can put their ACC Systems Inc. ACC570 handheld reader in "Geiger counter" mode and walk through the space station, listening as the beeps emitted by that device become louder and more frequent the closer they get to the tagged item being sought.
For a dense reading environment, the smart drawer allows workers on the ground to prompt the cabinet via radio to read the tags of all items stored inside it. That information is then sent back to ground control, where personnel can view what is in the cabinet and determine if anything is potentially running out.
JSC and NASA's Ames Research Center are jointly investigating a robotic free-flyer with a built-in RFID reader. This free-flyer would float through a region of the space station, capturing RFID tag reads as it does so. It comes with a propellant; its course can be programmed into its onboard computer, and the system then links its location with the RFID read data, in order to identify what is found at any given location.
According to Fink, JSC is currently considering RFID reader alternatives to reduce crew labor, while at the same time reducing the need for fixed RFID readers that increase the number of cables onboard and take up power outlets. "Having conventional readers and cables everywhere," he says, "is not an option for future deep-space missions, primarily due to mass [size] constraints."
JSC has also developed a container that utilizes RFID-based sensors to detect how many items, such as pills or Band-Aids, are stored inside it, and that data can then be transmitted to a reader via a UHF RFID tag attached to that container. Fink declines to explain how the system determines how many items are in a particular container.
In addition, the space agency is investigating tags with extended read ranges, which were initially developed for possible use on lunar missions. JSC had been looking into a passive UHF RFID tag with a longer read range, which could be used to provide navigation aid for the lunar lander or vehicles traveling across the Moon's surface. The tags could be spread on the surface of the Moon, and a reader on the vehicle could capture the ID numbers while JSC software determined the vehicle's location according to those reads. Fink says there may still be additional needs for a tag with a long read range, and the JSC is working with partners to develop an RFID tag that employs an array of antennas on tags to extend the read range and produce additional power for the tag—for example, when attached to a sensor.
The agency has determined that much of its development—the smart drawer, for instance—has potential use cases in the commercial sector, such as health care. Fink says JSC is currently in conversations with potential end users in health care and other markets regarding the technology.
