In Part 1 of our series on COTS components for space applications, we discussed why the government is increasingly turning to “commercial off the shelf” parts for spacecraft, satellites and more. COTS parts have already been successfully adopted in many military applications, but when it comes to space, COTS adoption has been much slower.
Space exploration has never been cheap. In the days of the Apollo program, the cost of sending payloads into space was such that only government agencies with billions of dollars to spend could afford it. Over time, those costs have begun to come down, but even with advances in launch technology, funding for such activities ebbs and flows. In the wake of budget cuts for military and aerospace Research and Development, there has been much pressure to develop systems and designs that meet the needs of space projects and reduce costs without sacrificing quality. This is where COTS (Commercial Off-The Shelf) products offer a potential solution.
The critical component that is becoming more of a necessity for cubesatellite platforms is the GPS Disciplined Oscillator, GPSDO for short. GPSDOs comprise of a GPS receiver, Oven Controlled Crystal Oscillator (OCXO), and a Phased Locked Loop (PLL). In this post, you'll get a deeper look into how GPSDOs are designed to help achieve mission success for your small satellites or cubesatellites.
The Global Navigation Satellite System (GNSS), in geo-stationary orbit, provides a GPS signal that many use today on the ground for navigation. With a GPS receiver (along with a GPS antenna) in place on board the satellite, a very precise 1 pulse per second signal can be generated from the signal transmitted from the GNSS (10-12 depending on how well the GPS receiver was designed).
With the 1PPS signal from the GPS receiver, the OCXO can be steered using a phased locked loop. The PLL essentially compares a PPS signal derived from the OCXO to the 1PPS signal generated by the GPS receiver and a control circuit adjusts the OCXO frequency to synchronize both signals at the same timing offset (or phase). The GPS receiver is a great solution for long-term stability because OCXOs degrade over time with respect to stability, known as aging (i.e. increase in deviations over time from the desired frequency), and over temperature as well.
This degradation is being compensated over time with the control circuitry in the PLL which that adjusts the frequency of the OCXO as the PLL is locking the derived PPS signal from the OCXO to the GPS 1PPS signal. However, short-term stability on the 1PPS signal from the GPS receiver is quite noisy due to atmospheric fluctuations, jitter within the GPS receiver, and other noise contributors. The use of a very stable OCXO for the GPSDO remedies this issue (ultra-stable quartz OCXOs can have short-term precision on the order of 10-12 or 10-13).
The GPSDO design enables for a great short-term stability (from the OCXO) and long-term stability solution (from the 1PPS GPS signal). A system block diagram is provided below:
Small satellites have grown dramatically over the past decade... and they are still growing fast and furiously. In this post, you'll learn about how to achieve mission success for satellites and how GPS Disciplined Oscillators (GPSDOs) can do the trick.
Satellite communication touches our lives in ways most people don’t fully appreciate. From GPS to satellite TV to the communication networks that make modern economic, military and political affairs possible, there are few areas of life that the rise of SATCOM technology has not shaped in some way, directly or indirectly. While visions of massive arrays and constellations might be the first thing that comes to mind when some people think of satellites, today we’re going to focus on something a little less visually impressive but just as important; the Very Small Aperture Terminal, or “VSAT.”
Podcasts have never been more popular. Whether you are commuting, in the gym or just relaxing at home, they’re a fantastic way to stay on top of personal interests as well as developments in your industry. For engineers and project managers working in the RF industry, some of the biggest growth is expected to occur in the field electronic warfare, which is slated to become a nearly $20 billion industry by 2026. To help you gain a sense of where the electronic warfare industry and the defense sector as a whole are headed in the near and long-term, we’ve compiled a list of some of the best podcasts relating to these topics.
While the expansion of the private sector into space is still in its infancy, there is little doubt that it will prove to be one of the most significant economic developments of this century, and RF engineers are one group of industry specialists that are making it happen. Indeed, it's almost impossible to overstate the impact that engineers specializing in radio frequency tech have had and will continue to have, not only with operating and maintaining commercial space activity but shaping it as well. Let’s explore all the different ways that RF engineers are making the “Space 2.0” era possible.
So much of the focus in SATCOM technology pertains to what goes on in outer space, but what happens down here on earth is just as important. The fact is that every satellite, no matter how advanced, is still only a part of a larger system. Today, you'll learn the important role that satellite ground stations play in making SATCOM possible, and some of the challenges (and possible solutions) for organizations working with LEO satellites on the ground.
Electronic warfare is one the defining characteristics of modern combat. Its origins can be traced back the First World War when Allied and Central Powers began intercepting and interfering with each other’s radio transmissions, and it has advanced at a staggering pace ever since. Today we’ll examine 3 of the most significant milestones in the evolution of electronic warfare technology, and discuss what the near future holds for this exciting and increasingly important military specialty.
The average person probably doesn’t spend any time thinking about satellites unless he or she is specifically entering an address into a GPS device— and even that would be a stretch. Satellite communication has become such a pervasive, omnipresent influence in our lives, our economy, and our government that we simply take it for granted. With the advent of high-throughput satellites (HTS), this trend has only increased. Speeds and data capacities never before dreamed of are becoming commonplace, and dramatically improving SATCOM capabilities in both the public and private sectors. A core technological attribute that is enabling the HTS revolution is a technique called beam hopping.