Overview: Here you'll learn all about how information processing works and how the flow of data and information through a spacecraft works and lots of other cool stuff. You'll see the flow of data from the ground and through a satellite and it's communication with people on the earth.
Information Processing: Introduction
- Since the beginning of human history, people have found the need to communicate over long distances
- As the distances grew and the number of things that had to communicate grew, the ways people communicated changed. New technologies were continually developed and discovered to help humans communicate over longer and longer distances and send more and more information.
- Most of the time when we communicate with one another we only tend to think about what we see or hear or read.
- Most of the time we do not stop to think about how the information we get actually gets to us.
- For space missions, a team of engineers and technicians is typically dedicated to figuring out how to relay information from a spacecraft to various places and getting it to the people and machines and computers that the information needs go to.
- The processes and steps the engineers and technicians use to transform information for various destinations is known as "Information Processing"
II. Review of Space Communication Concepts
- In the Space Communication training module we discussed many items related to relaying information from a spacecraft back to earth. Even if you didn't take or complete the Space Communications training module we'll review some key concepts now that will help us explain data processing.
- In the Space Communications training module we showed that for Low Earth Orbit missions, a spacecraft could transmit its data directly to a ground station or use the NASA Tracking and Data Relay Satellite System to relay its data back to Earth.
- We also showed that in several cases the transmission of data from a spacecraft could be interrupted because the spacecraft could not "see" or have a line-of-sight to the ground station or Tracking and Data Relay Satellite.
- In this training module we'll take a closer look at how the data that is transmitted from the spacecraft, called telemetry data, is collected, package, transmitted, unpackaged and delivered to its final destination.
III. Spacecraft Instruments and Systems
- On board most every NASA spacecraft, either manned or unmanned, are numerous scientific instruments and spacecraft systems that generate data on their own or are monitored by sensors that generate data.
- Some of the telemetry data generated is only used onboard the spacecraft but most of it is sent to the ground so technicians, engineers and scientist can determine if the spacecraft systems and science instruments are healthy and working properly. This type of telemetry data is often called "state of health" information or sometimes "housekeeping" data. This data may be as simple as the voltage on circuit or as complex as the biometric data on an astronaut.
- Another portion of the data that is sent to the ground is used by Operations personnel to determine if the spacecraft computer systems are carrying out the proper instructions to make the spacecraft perform the mission that it is supposed to be doing.
- The last major component of the data sent to the ground is the data generated by the science instruments. This data may represent things such as the wavelengths of light from a star, the composition of the atmosphere of a planet, or even properties of fluids in a super-cold state flying in a micro-gravity environment
- The one thing in common with all the data generated is that it is collected, recorded, packaged for transmission by the Command and Data Handling or C&DH system onboard the spacecraft.
IV. Spacecraft Command and Data Handling Systems
- As the name implies, a spacecraft Command and Data Handling System has two primary jobs. The first is to receive and relay or execute commands and instructions in order to operate the spacecraft. Its other job which is the focus of this lesson is to collect and transmit data to the ground.
- To perform its data handling job, a C&DH system typically uses two primary components. The components are a computer or Central Processing Unit (CPU for short) and a recording device which is typically a Solid State Recorder. The C&DH system also works in connection with a radio frequency communication system or RF system to receive commands and send data to the ground.
- The CPU performs the majority of the data collection by requesting information from and listening to the spacecraft systems, sensors, and instruments. This job is similar to a mailman collecting mail from mailboxes at homes, businesses, and other locations. A big difference between the job of the CPU and the mailman's job is that the CPU typically must also wrap up the data in a package and put the correct delivery address information on the package.
- Just like you see at a post office, the packages of data can come in many different sizes which are determined by the contents of the package. A CPU may sometimes have to deal with thousands of different packages each with different identifying and delivery address information.
- Just like a mailman's truck is relatively small, a CPU can only collect a limited number of packages before it must drop them off at a larger storage location before they are sent or transmitted to its final destination. A C&DH CPU will temporarily store small amounts of collected data and then move it to a Solid State Recorder which can hold a much larger amount of data.
- When there is a ground contact, the Solid State Recorder will playback its recorded data so that it can be transmitted to the ground via the RF system. As is shown in the Space Communication training module, the times when the RF system can transmit data is determined by when the transmitting spacecraft can "see" the receiving ground-station or relay satellite.
- When a transmitting spacecraft is sending data to a relay satellite or ground stations certain pieces of information are of such importance and priority, they are collected by the CPU and sent to the RF communication system immediately for transmission. This type of data is often called "real-time" data because it is data that is not delayed before being sent.
- Whether data is sent via a relay satellite or not, the data's first stop on Earth is at a Ground Station
- In the early days of NASA, the only way to communicate with a spacecraft was through a ground-station receiving information directly from the spacecraft. Because a spacecraft's flight path circles the entire earth, ground-stations had to be located all over the globe
- With the deployment of the Tracking and Data Relay Satellite Systems or TDRS, NASA's dependence on numerous ground-stations diminished, but several key ground-stations are still an essential part of NASA's communication infrastructure
- NASA's Space Network which handles communications with earth-orbiting spacecraft through the Tracking and Data Relay Satellites maintains three primary ground facilities. They are the White Sands Ground Terminal (call letters WSGT) and the Second TDRS Ground Terminal (call letters STGT), both located in Las Cruces New Mexico, and the Guam Remote Ground Terminal (call letters GRGT) located on Guam Island in the Pacific Ocean.
- The NASA Deep Space Network handles communication with interplanetary spacecraft. The primary ground-stations for this network are located near Goldstone, California; Madrid, Spain; and Canberra, Australia.
- And finally NASAs Ground Network is composed of a number of facilities which will support communications directly to an earth orbiting spacecraft. Ground Network facilities are located in Norway, Antarctica, Alaska, Florida, and Virginia.
VI. Ground Station Data Capture and Processing
- Although NASA maintains several ground-stations, each of which has unique capabilities and assets, the general flow of data through a ground station is the same
- As the RF signal from a spacecraft is received by a ground station antenna the signal is forwarded to a computer that collects the data from the RF signal. You can think of this as a postman taking all the mail they have collected out of their truck and taking it into a post office for sorting.
- Like a letter or a package sorted at a post office, the data packages or data packets as they are called, are sorted into groups. At a post office, letters and packages destined for the same zip code are grouped together. For spacecraft data, the data packets are grouped into "Virtual Channels".
- At least one Virtual Channel, that is a group of data, is designated to collect real-time data. The real-time data is sent immediately to the Mission Operations Center that controls the spacecraft. The data in other virtual channels is recorded at the ground station and sent to the Mission Operations Center later, typically within a couple of hours.
VII. Mission Operation Center Data Processing
- At the Mission Operations Center, or MOC for short, other computers sort through the data packets in each virtual channel and perform steps to make the information in the data packets usefol to engineers and scientists.
- For example, data that is used to monitor the health of spacecraft systems is converted from raw values like the voltage output of a thermal sensor to a temperature measured in Fahrenheit or Celsius, and displayed on a computer screen or written to a report
- At the MOC, engineers who are knowledgeable about how the spacecraft systems are expected to perform review the "housekeeping data" to make sure the systems are working properly.
- The science data from the spacecraft is typically sent to a Science Operations Center where the scientists and researchers will examine the science data in a variety of ways. How the science data is used depends on the type of investigations that are being pursued.
VIII. Earth Science
- Now you have a basic understanding of how satellite data is collected, stored, processed, transmitted, and distributed. At NASA’s Goddard Space Flight Center, scientists collect data from satellites of various missions to study our own planet as well as space. Let’s look at some examples of information processing in Earth Science.
- One of the topics in Earth Science is to study the climate and climate change of our own planet. Let’s look deeper at an example of how hurricanes are tracked by NASA in cooperation with other agencies using information processing.
- NASA and NOAA use many different satellites to monitor and track hurricanes. However, one of the most important satellites is the Geostationary Operational Environmental Satellite series (GOES). Each satellite in the GOES series supports two major instruments: an Imager and a Sounder. These instruments resolve visible and infrared images, as well as temperature and moisture profiles of the Earth's atmosphere. The satellite continuously transmits this data to a ground terminals where the data is processed and rebroadcast.
- Using the data acquired from the satellite, the Satellite Operations Control Center (SOCC), in Suitland, Maryland generate commands that are sent to the satellite through the ground facility in Wallops, Virginia to support daily satellite operations, as well as special events like tracking hurricanes and tornado.
- The ground station also provides instrument data processing. For each operational GOES spacecraft, the ground system digests the raw instrument data stream and generates a processed data stream.
- That processed data is then transmitted to the spacecraft for rebroadcast to the primary weather system users. Computers at Maryland in the Environmental Satellite Processing Center (ESPC) also receive the data and it is turned into information that is sent through the Internet to users. Information like wind speed and direction, cloud height and motion, rain fall intensity, fire location and intensity, are created from the GOES data.
- Now let’s look at an example of Space Science information processing with the SWIFT mission that studies gamma-ray bursts, the most powerful explosions in the universe.
- In order to study events called Gamma Ray Bursts in the Universe, NASA developed and launched a spacecraft called Swift.
- Gamma Ray Bursts are bursts of massive amounts of energy that have been observed to occur all over the sky. Scientists speculate that Gamma Ray Bursts occur when two Nuetron Stars collided and form a Black Hole or when a single star that is very massive (more than 40 times massive than out Sun) explodes.
- The Swift spacecraft was designed with special instruments and systems that allow it to detect Gamma Ray Bursts and maneuver rapidly to look at the burst.
- A unique feature of the SWIFT mission as it relates to data processing is that as soon as a Gamma Ray Burst is detected, the SWIFT spacecraft determines the celestial location of the explosion and sends out an alert to notify ground-based and space-based observatories that it has occurred. Since it is the very early stages of the burst that scienists and researchers are interested in studying, the notification from Swift must come rapidly.
- When a Gamma Ray Burst is detected, an alert is transmitted to the Tracking and Data Relay Satellite System that dowlinks the alert to the ground station in Las Cruces, New Mexico or the ground station on Guam. The alert is forwarded to a facility at Goddard, Maryland, then distributed over the internet to the Gamma Ray Burst Coordinate Network.
- Science data collected by Swift is downlinked through a ground-station in Malindi, Kenya and routed to the MOC located at Penn State University for processing.
- The science data is then distributed to three science centers located in the United States, the United Kingdom, and Italy
- For every space mission, a dedicated group of technicians and engineers work diligently to make sure the data collected reaches the scientists, teachers, students and other people who need to use the data.
- The jobs they do and the tools they use are crucial to
- Collecting data -
- Addressing it -
- Storing it -
- Transmitting it -
- Sorting it -
- And delivering it -
- So next time you take time to admire a beautiful photograph from space, or use data from a space science instrument, think about how you got the information.
Fly It!: Introduction
Here we will test your understanding of the Information Processing training for the Fly It! Module for Information Processing. You will be tested on the various sub-systems involved in all phases of the data flow, from instrument capturing the data to the ground station receiving the data. Then you will be interactively tested on handling the data packets within the C&DH system using Robbie the robot helper. Good luck!
Phase 1 - Sub-systems are inititiated...
You are presented with a list of five empty slots and five sub-system boxes for you to enter into the appropriate slots. The correct data flow in steps one through five are: Instrument, C&DH, SSR, RF, and Ground Station. Success with Phase 1 leads to Phase 2.
Phase 2 - Let's zoom into the C&DH Sub-System, and find our robot helper, Robbie the Robot.
He helps us sort between Science Data, Real-time Data, and System Health Data. There are four different types of packets and Robbie sorts them into the correct virtual channels. After successful completion of Phase 2, the communication linkup is successful and your data is sent to the ground. A video plays showing a series of low-earth orbit satellites communication with each other successfully and to the ground stations because you have successfully completed the mission.
Conclusion - We hope you have learned a lot about Information Processing. Please visit the Space Operations Learning Center home page for more training modules and a lot more for you to learn.
[Back to Top!]