COTS in space? Not so fast, say some rad-hard designers
The role of commercial off-the-shelf (COTS) parts fielded in satellites and other space applications remains a hot topic as the demand for low-cost nanosatellites grows. COTS signal-processing designs are also attractive to military space system designers, but they fear the reliability of such components in long space missions.
Budget constraints, demand for inexpensive small satellites, and other issues are forcing space-platform designers to consider using COTS components for space, but COTS parts may not be appropriate or desirable for all space missions.
The market is open to the idea of using COTS in space. “This whole concept of building large constellations with COTS components, we refer to it as ‘new space.’ I’ve also heard it referred to as Space 2.0,” says Ken O’Neill, director of marketing, space, and aviation for Microsemi’s SoC Products Group in San Jose, California. “We are in dialogue with many companies who are proposing to create systems along the lines of using commercial parts and we are doing what we can to support it. We also have to acknowledge the reliability of such systems is going to be the proof of the pudding. Everyone is waiting to see if they can create a constellation with cheap commercial products.”
Budget constraints may be the driving factor for designers of space applications to find new ways of addressing the challenged posed by COTS components. The reality: Military officials want COTS components in applications where cost needs to be reduced. However, using COTS components where radiation-hardened components are required becomes more of a challenge to implement, versus spending the money in order to have a high-reliability system.
“COTS components put a burden on the design team in order to do mitigation on the part,” O’Neill says. “There are mitigation techniques that are in the open domain – redundancy and using spares – those are the two things that you do to mitigate.”
However, even using mitigation techniques, “You have to put more parts into the system than you would have otherwise,” he continues. “If you were using a COTS part, you would need to put triple-redundancy parts into this. That presents some challenges from the perspective of board space and power consumption. Now you have to supply power to three parts instead of one.
Using COTS components in space translates to more work: “Even worse,” O’Neill continues, “you also have to put some kind of voting and control mechanism, a system that monitors activity and makes a decision that one of the parts has an upset or is transient and that renders it inoperable, which needs to be reset. Something has to be a watchdog on there. That’s an extra component that needs to be powered and consumes board space.”
Extra processing steps would have to be taken to make COTS components meet rad-hard requirements. Therefore, “most of the customers we are talking to today are leaning towards traditional, high-reliability hermetic ceramic packaged products to use in space,” says Larry Longden, vice president and general manager at Data Device Corp. (DDC) in San Diego, California.
There are still pros to using COTS components. “COTS to me has always had the ability to have a product on the shelf versus having to build to order,” says Chuck Tabbert, vice president of sales and marketing at Ultra Communications in Vista, California. “The advent of the Qualified Manufacturing Line (QML) system has made it possible to have companies build products to forecast and qualify the fabrication line versus building to the next order that comes in the door and running a lot-specific qualification.”
Space applications need to last for a few years in orbit. “With small satellite constellations, they’re mostly in low-Earth-orbit (LEO) applications, chasing the ‘Internet in the sky’ mobile communications and Earth observation markets,” he continues. “The mission profile will probably not be that of the geosynchronous constellations and therefore the radiation requirements for these LEO applications will be less severe.”
Mission-specific small satellites
COTS components might be the answer for small satellites that are mission-specific only. “In recent years the U.S. military has had their own initiative on smaller satellites, with the intent to reduce launch costs and the time taken between making a decision to create a satellite to fulfill a mission and “getting that satellite in orbit,” O’Neill says. “The military runs the program called Operational Responsive Space (ORS), which is managed by the Air Force Research Laboratory (AFRL). There have been a number of ORS satellites already built and launched. Other, experimental, satellites have already been developed and launched, some of which have intended to see what can be done with small form factors.”
Tabbert asserts that in order to make COTS components successful in space, rad-hard semiconductor folks [must be able] to anticipate what products will be selling in the small satellite market, keep the line qualified, and have products on the shelf in-house or at distributors, as well as keep the unit price competitive.
The good news about the military is that “they will use whatever they can to get the job done – be it small satellite constellations, to hosted payload applications, to standard GEO and MEO constellations,” he continues. “With rumors of nation-states developing anti-satellite capabilities, it just makes sense to diversify one’s assets on numerous platforms so no one strike can take down a capability. Small sat constellations have their place for certain missions.”
The lure of high-end signal processing
COTS components are attractive because they offer so much in terms of bandwidth and performance. “The design community in radiation-hardened electronics is really working on solving the big signal-processing challenge,” O’Neill says. “The issue is that satellite operators are looking for an increased amount of information to come from their space assets, whether it’s remote sensing satellites, imaging, radar, or spectrometry.”
High bandwidth demands in satellite applications dictate the path designers take with rad-hard electronics. “The industry is leaning towards higher density memory products and higher speed A/D or D/A converters, along with more high-speed interface options,” Longden says.
Also commanding attention is the need for speed. “Intra-satellite data-transfer bandwidth requirements are exploding. Point-to-point solutions between sensors and instruments to flight computer to mass-memory storage requirements are requiring 40 [Gigabits per second] Gbps transfer rates, which will increase to 100 Gbps in the next three to five years,” Tabbert says.
Because of the high demand, “hardened- [field-programmable gate array] FPGA manufacturers are struggling to keep up. The need for 10 Gbps to 25 Gbps per channel connectivity is coming quickly,” he adds.
The ultimate goal of these parts is “to be able to store and process all the data that [operators] are connecting on satellites. It’s a tremendous amount of data, and they need faster and bigger memory to do that,” Longden says. “As well, they need faster and more accurate conversion products to be able to read that data from different analog systems.”
One such memory product is DDC Microelectronics’ NAND-Flash memory, aimed at reaching those high-density, high-speed memory requirements for space. (See Figure 1).
Another example of a product intended to meet the high-density, high-bandwidth data demands of space is Microsemi’s RTG4 board (see Figure 2). “It is intended to satisfy that demand for onboard signal processing. It has more logic resources and it’s got more multiply-accumulate blocks,” O’Neill says.
Taking advantage of signal processing innovation today also means leveraging standards. “We are seeing a lot of industry involvement in standards such as SpaceVPX,” says O’Neill. “It’s a standard that has a lot of industry alignment behind it,” he says. The standard “provides form factor and interconnect standards for board-to-board communications. In space systems, designers are using serial interconnects – 2.5 Gbps, even some as high as 3 1/8 Gbps, per lane – and of course those lanes can be ganged together,” O’Neill adds.
Standardization evens the playing field. Moreover, says Michelle Mundie, business area director, standard products, at Cobham Semiconductor Solutions in Colorado Springs, Colorado, “Leveraging open standards will enable more capabilities for the sensor payload. The SpaceVPX architecture of interconnects drives the standards for performance. New products can interconnect with one another to achieve performance. Standardizing the platforms will reduce design complexity and cost.”
Cobham Semiconductor Solutions’ UT64CAN333x series of Controller Area Network (CAN) transceivers are designed to manage rates ranging from 10 kbps to 8 Mbps; all are designed in accordance with the ISO 11898-2/-5 standard (see Figure 3). “Cobham is focusing on rad-hard by design and rad-hard at process techniques while also addressing size, weight, and power (SWaP) requirements,” Mundie says. “This angle allows the company to look at different technology notes and interconnect architectures in satellites.”