Commentary | Reinventing Space: Dramatically Reducing Space Mission Cost — Ground Segment and Operations
This is the 11th in a series of articles on how to go about dramatically reducing space mission cost while maintaining a high level of mission utility. Chronologically, mission operations represents the end of the mission life cycle, but it is also what the mission is all about — generating or communicating data and information that are intended to make it all worthwhile for the end user and whoever devoted a very considerable amount of money and time to create the space system and put it in orbit or at its intended destination. It is mission operations that brings down the data that support the warfighter, the scientist or the commercial user, that makes sure the spacecraft remains healthy throughout the mission life, and that disposes of the spacecraft at end of life so as to ensure that it doesn’t harm people or the environment or contaminate other worlds. Although operations is critically important, we want to do this job as economically as possible, consistent with achieving a high level of mission utility.
Use Single Shift Operations
Traditionally, mission operations has been an expensive and complex activity run from a mission operations center requiring multiple people and 24-hour coverage, seven days a week. This, in turn, implies either four or five operations teams and the management and communications needed to make them work smoothly together. The most direct approach to reducing operations costs is to reduce the operations crew to a single shift of 40 hours a week. This reduces the number of people, overhead, management and communications costs. It also requires that the spacecraft be capable of “taking care of itself” for an extended period, including probably long weekends and holidays. Ordinarily this is much easier with small spacecraft that have large design margins and are capable of at least maintaining themselves in nearly any orientation. Historically, many small spacecraft have been operated by one person on a very part-time basis. Much of the process of reducing operations cost is ensuring the spacecraft doesn’t need continuous care and feeding and can call for help whenever it needs it. The level and sophistication of automation, both on the spacecraft and on the ground, have increased dramatically in recent years. As a result, the potential for leaving the spacecraft alone for extended periods has become much easier, much more economical and much lower risk.
Use Service-provided Operations
Another approach for reducing operations cost is the use of service-provided ground stations. Here we are making use of existing ground stations located around the world that are both manned and maintained in order to communicate with multiple spacecraft. This also provides a high level of redundancy and excess coverage. The main disadvantage is that you have to share priority with others. However, this can be overcome by complementing the service-provided system with dedicated remote antennas built specifically for your system. When used in conjunction with a service-provided system, these remote sites are not required to have near-100 percent reliability, because the other ground stations provide backup and coverage in areas beyond the reach of one or a few dedicated remote antennas. Generally, the cost of the service-provided system is in the range of several hundred dollars per data pass, which is usually a great deal less than maintaining a dedicated ground system. Looking at the dedicated ground station from a cost perspective, we have to account for not only the cost of staffing and maintenance but also amortization of the cost of creating it in the first place.
Fly the Spacecraft over the Internet
In conjunction with service-provided systems, there is the potential for simply flying the spacecraft over the Internet. This is done by using the service-provided system for communications between the satellite and the ground. The ground station then puts the data on the Internet, from which they are then downloaded by as many end users as need them. (A variety of encryption techniques are available that keep the data secure, if needed.) Commands are sent to the spacecraft via the same process and, again, can be encrypted to avoid others intentionally or inadvertently taking over the spacecraft. In this way, the spacecraft becomes effectively just another node on the Internet that you can talk to, get data from, and control from any location where Internet access is available.
Use the Internet for Data Delivery
Similar to the process above, the Internet is nearly an ideal mechanism for delivering data nearly instantaneously to multiple end users in one location or scattered over the entire world. Because Internet use has become nearly universal, this also means that essentially all of the end users will understand the data communication process or can be quickly brought up to speed. Similarly, data archiving becomes simply a matter of creating the process for backing up the computer data with whatever regularity and safety is needed.
Use Autonomous On-board Orbit Control
One of the more cumbersome and critical ground station functions is maintaining the spacecraft orbit, particularly in low-altitude orbits where atmospheric drag is high. This can be accommodated by using a GPS receiver for navigation and autonomous on-board orbit control. One of the major problems faced by the originalconstellation of 66 satellites plus six spares, and one of the major drivers of early Iridium operations cost, was the need to do orbit determination several times per day on each of the satellites and, based on the results, do orbit station-keeping maneuvers commanded from the ground. This process and the associated costs go away entirely when the process is done autonomously onboard the spacecraft, in the same fashion that attitude control has normally been done autonomously onboard since the beginning of the space program. A secondary advantage of this approach is that you will know in advance (years in advance, if desired) just where your spacecraft is located at any given time in the future to about 1 kilometer in-track and even more precisely in cross-track and radial. This means that open-loop pointing of ground antennas will be reasonable for almost all applications and communications links.
Use AMSAT for Ground Communications
Finally, another approach is to use amateur radio satellite organization (AMSAT) resources for science data return. This approach of making use of the amateur community has worked in astronomy for more than a century as amateur astronomers make most of the observations of variable stars for which it is simply too expensive to tie up the manpower and resources of professional astronomers. (The American Association of Variable Star Observers has been in continuous and very successful operation since 1911.) This not only would provide data return at much lower cost, it also would create a high level of interest in multiple communities where amateurs were collecting useful science data and genuinely helping in the exploration of space.
The 12th and final article in this series will summarize the overall process of reducing cost and how to go about creating much lower cost missions while maintaining a high level of mission utility.
James R. Wertz is president of Microcosm Inc. He is co-author of “Reducing Space Mission Cost,” published in 1996, and has been teaching a graduate course at the University of Southern California on that topic since then. If you have questions, comments or suggestions, or simply want to discuss these issues, he can be reached at firstname.lastname@example.org. Information on the joint Microcosm/USC Reinventing Space Project can be found at www.smad.com/reinventingspace.html.