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Overview of the capabilities of long duration balloon flight ground station equipment of the national scientific balloon facility
Advances in Space Research 33 (2004) 1623–1626 www.elsevier.com/locate/asr
Overview of the capabilities of long duration balloon flight ground station equipment of the national scientific balloon facility S. Breeding *, B. Stilwell National Scientific Balloon Facility (NSBF), 1510 East FM 3224, Palestine, TX 75801, USA Received 19 October 2002; received in revised form 14 June 2003; accepted 18 July 2003
Abstract This paper presents a brief overview of the NSBF ground station equipment (GSE) systems used for long duration balloon (LDB) flights. It concentrates on the handling of scientific data and how scientific GSE systems are interfaced with NSBF GSE systems. Ó 2004 COSPAR. Published by Elsevier Ltd. All rights reserved. Keywords: Scientific ballooning; Capabilities of long duration balloons; Ground station equipment; National Scientific Balloon Facility
1. Basic LDB flight communications scheme A simplified view of the basic LDB flight communications scheme is shown in Fig. 1. The balloon carries a payload consisting of various NSBF control and communications equipment and the science equipment. The remote operations control center (ROCC) is usually located at or near the launch site. While the balloon is located within line of sight (LOS) of the ROCC facility, the ground station equipment at the ROCC can be used to send commands to and receive low rate science data and housekeeping data from the payload. (The high rate science data is only available via TDRSS. Thus, it is only received at the OCC computer in Palestine.) The operations control center (OCC) is located at the NSBF site in Palestine, Texas. If a TDRSS (NASAÕs tracking and data relay satellite service) link is available and scheduled, the OCC can be used to send commands to, and receive high and low rate science data and housekeeping data from the payload. Any OCC or ROCC computer can be configured as a server and/or a client for housekeeping data. This allows an OCC or ROCC to
* Corresponding author. Tel.: +1-903-723-8008; fax: +1-903-7238082. E-mail address: [email protected] (S. Breeding).
share important state of health data with other OCC/ ROCC computers. Fig. 1 does not include various additional data and command systems available such as HF radio, Argos, Inmarsat and Iridium telephone.
2. NSBF OCC site overview The NSBF OCC facility houses four virtually identical OCC GSE computers. Each is able to support one balloon flight. The OCC computers log all incoming data and outgoing commands. The OCC site also has two identical NDISC (NSBF data interface service capability) computers. One acts as the primary computer and the other acts as a backup. The NDSIC computer can support up to four simultaneous flights. The NDISC computer logs all incoming TDRSS data. The OCC site also houses legacy TDRSS POCC equipment that can support two simultaneous flights. All flight control can be managed from the OCC site, including flight termination. All communications are secure as the OCC GSE computers are protected by a firewall and the NDISC and legacy POCC equipment connects to the outside world via NASAÕs Closed IP Operational Network (IONet). During an LDB flight, operators are on duty 24 hours a day. A large UPS and a generator protect the OCC building power.
0273-1177/$30 Ó 2004 COSPAR. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.asr.2003.07.035
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S. Breeding, B. Stilwell / Advances in Space Research 33 (2004) 1623–1626
Fig. 1. Basic LDB flight communications scheme.
3. OCC and ROCC site computer hardware Each of the four OCC GSE computers have a single board computer with dual, 500 MHz Pentium III processors, 384 Megabytes of SDRAM, a 16 serial port Digiboard, a 10/100 network card, a 21 inch flat screen monitor, 9 Gigabyte removable hard disk drive and a read/write CD drive. The operating system is Windows 2000. The ROCC computer hardware is identical, with the exception that the monitor is only 17 inches. The main and backup NDISC computers are very similar. They have no Digiboard, they share a single 17-inch monitor, their hard drive is only 4 Gigabytes, and they have a DAT40 tape drive rather than a read/write CD drive.
4. OCC and ROCC site computer software All NSBF software for the OCC and NDSIC computers is written with National InstrumentsÕ LabVIEW
graphical programming language. LabVIEW is a high level language. It is well supported, easy to learn, and it is a good fit for the electrical engineering mind set. It has a feel very similar to drag and drop schematic capture programs. Engineers with experience with these hardware tools tend to find LabVIEW easy to use and familiar. 4.1. OCC/ROCC GSE computer software The NSBF OCC/ROCC software is modular and configurable. Configuration information is stored in an initialization file which is accessed at startup to define which modules are loaded, port assignments, addresses, etc. The operator can also make configuration changes interactively. As changes are made the initialization file is updated, insuring that the file always reflects the current configuration. If the software should ever need to be restarted, it will be configured the same as it was before the restart. The software design makes liberal use
S. Breeding, B. Stilwell / Advances in Space Research 33 (2004) 1623–1626
of state machines. These are easy to understand and tend to be very deterministic. Thus the software is stable and reliable. The modular approach keeps the software efficient. Unneeded modules are not even loaded. For example, at the OCC there is typically not a LOS radio link but the TDRSS link is vital. Thus, the LOS command and data modules are not loaded on the OCC machines while the TDRSS command and data modules are loaded and run. At the ROCC machine there is no TDRSS link, but the LOS links are vital. In this case, the TDRSS command and data modules are not loaded, while the LOS modules are loaded and run. A very powerful tool of the OCC/ROCC software is the client/server capability mentioned earlier. For example, it is common for the balloon to fly out of line of sight range from the ROCC site a few days after launch. Typically, the OCC computer continues to communicate with the payload via a TDRSS link. In this case, the OCC computer is configured as a server and the ROCC is configured as a client. The ROCC then receives housekeeping data updates periodically (usually every 30 s) from the OCC computer. Thus, the operations personnel at the ROCC can monitor flight details even when their communication links with the payload are no longer effective. The operator interface for the OCC/ROCC software is designed to quickly inform the operator of problems or potential problems. The various information screens use color-coded displays to indicate acceptable (green), caution (yellow), or warning (red) states of specific parameters. The level definitions are configurable via setup files, so they can be changed with different flights. 4.2. NDISC computer software The NDISC computer software is a fairly new tool at NSBF. It is designed to interface with WDISC (WSC data interface service capability) in White Sands. The NDISC machine and its software are designed to support up to four simultaneous flights. The software is not as modular as the OCC/ROCC software as the tasks are not as configurable. The main configurable portions of the NDISC system are modules dealing with specific flights. For example, if only one flight is active then only one set of TCP-IP link support modules are loaded and run. If all four flights are active then four sets of link support modules are loaded and run. The main run screen of the NDISC software is very simple and easy to understand. Color-coded icons tell the operator when specific forward and return links are active (green) or inactive (red). If a link failure occurs it is a very simple step for the operator to click on a single button to fail over to the backup links.
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5. Science interface details See Fig. 2 for a simplified look at science communications for LDB flights. The science OCC computer, located in the lower left portion of Fig. 2 , is connected to the NSBF OCC computer via two serial ports. One is a 2400-baud command connection. The science computer issues commands to and receives command responses from the OCC computer on this serial port. The second serial connection is a 19200-baud data input only connection from the OCC computer. The OCC computer writes high rate and low rate data, as well as low rate information from the optional science stack out this port. Both of these ports are simple, three-wire connections (no flow control, just transmit, receive and ground). The science OCC computer is usually unmanned, so it is typically connected to the Internet via a firewall. The science OCC computer runs some type of serial interface software to talk with the NSBF OCC computer. The science users connect to the science OCC computer via the Internet to retrieve data, issue commands, etc. The NSBF OCC computer is the primary operator interface for flight control. The operator uses it to check flight status, issue commands as needed to the balloon equipment, etc. The NSBF OCC computer sends control commands, and forwards science commands, to the NSBF NDISC computer via a rather complex TCP/IP socket connection. The NSBF OCC computer connects to the Internet via a firewall. Using this Internet connection it routes through the White Sands Complex computers, connecting to the NSBF NDISC computer via NASAÕs Closed IONet. Actually the NSBF OCC computer acts as a server and the NSBF NDISC computer acts as a client, so the NSBF NDSIC computer actually initiates the connection and periodically sends a command request packet to the NSBF OCC computer. The NSBF OCC computer then responds by sending all buffered commands to the NSBF NDISC computer. The NDISC computer forwards the commands to the WDISC computers at WSC for TDRSS transmission. The WDISC computers at WSC receive data from the balloon payload via the TDRSS satellite and forward it to the NSBF NDISC computer via a socket connection across the Closed IONet. The NSBF NDISC computer logs and forwards all TDRSS data received from WSC out an output only serial port at 19200 baud. The NSBF OCC computer receives this data and logs it. It then either forwards it to the science OCC computer (science data) or consumes the data for display or control purposes. The science payload computer located on the balloon gondola connects to the NSBF SIP flight computer via two serial ports. One is an output-only high rate data connection (19200 baud). The other is a bi-directional low rate serial connection (1200 baud). The science
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S. Breeding, B. Stilwell / Advances in Space Research 33 (2004) 1623–1626
Fig. 2. Simplified block diagram – TDRSS/WDISC science communications.
payload computer receives commands from the NSBF SIP flight computer on the low rate port. It also writes low rate data to the NSBF SIP flight computer on this port. The science payload computer writes high rate data to the NSBF SIP flight computer on the outputonly data port. If the science group is using the optional science stack, it communicates with the NSBF SIP flight computer at 4800 baud on a serial party line. The NSBF SIP flight computer receives commands from WSC via the TDRSS satellite and either consumes the commands as flight control functions, or forwards them to the science payload computer (science commands). The NSBF SIP flight computer forwards science data and NSBF SIP housekeeping data to WSC via the TDRSS satellite.
Higher gain results in higher signal-to-noise ratios for the communications signals. This results in a wider bandwidth and faster signals. While it is still being tested, it is hoped that it will allow data rates over 100,000 baud. If this does turn out to be true, then the serial rates for the two high rate data connections in Fig. 2 will increase to at least 115,200 baud. Another possible change might be to completely eliminate the serial data connection between the NSBF NDISC computer and the NSBF OCC computer. The data would be transferred using the already existing command TCP/IP socket connection.
5.1. New high gain TDRSS antenna
The NSBF LDB ground station equipment provides a reliable, versatile, and user-friendly interface to LDB flight payloads. On-going developments at NSBF continue to improve the performance and reliability of long duration balloon flights.
Personnel at Wallops Flight Facility have developed a high-gain TDRSS antenna for balloon flights. This antenna provides 18 dB of gain to the satellite signals.
6. Conclusions
Overview of the capabilities of long duration balloon flight ground station equipment of the national scientific balloon facility S. Breeding *, B. Stilwell National Scientific Balloon Facility (NSBF), 1510 East FM 3224, Palestine, TX 75801, USA Received 19 October 2002; received in revised form 14 June 2003; accepted 18 July 2003
Abstract This paper presents a brief overview of the NSBF ground station equipment (GSE) systems used for long duration balloon (LDB) flights. It concentrates on the handling of scientific data and how scientific GSE systems are interfaced with NSBF GSE systems. Ó 2004 COSPAR. Published by Elsevier Ltd. All rights reserved. Keywords: Scientific ballooning; Capabilities of long duration balloons; Ground station equipment; National Scientific Balloon Facility
1. Basic LDB flight communications scheme A simplified view of the basic LDB flight communications scheme is shown in Fig. 1. The balloon carries a payload consisting of various NSBF control and communications equipment and the science equipment. The remote operations control center (ROCC) is usually located at or near the launch site. While the balloon is located within line of sight (LOS) of the ROCC facility, the ground station equipment at the ROCC can be used to send commands to and receive low rate science data and housekeeping data from the payload. (The high rate science data is only available via TDRSS. Thus, it is only received at the OCC computer in Palestine.) The operations control center (OCC) is located at the NSBF site in Palestine, Texas. If a TDRSS (NASAÕs tracking and data relay satellite service) link is available and scheduled, the OCC can be used to send commands to, and receive high and low rate science data and housekeeping data from the payload. Any OCC or ROCC computer can be configured as a server and/or a client for housekeeping data. This allows an OCC or ROCC to
* Corresponding author. Tel.: +1-903-723-8008; fax: +1-903-7238082. E-mail address: [email protected] (S. Breeding).
share important state of health data with other OCC/ ROCC computers. Fig. 1 does not include various additional data and command systems available such as HF radio, Argos, Inmarsat and Iridium telephone.
2. NSBF OCC site overview The NSBF OCC facility houses four virtually identical OCC GSE computers. Each is able to support one balloon flight. The OCC computers log all incoming data and outgoing commands. The OCC site also has two identical NDISC (NSBF data interface service capability) computers. One acts as the primary computer and the other acts as a backup. The NDSIC computer can support up to four simultaneous flights. The NDISC computer logs all incoming TDRSS data. The OCC site also houses legacy TDRSS POCC equipment that can support two simultaneous flights. All flight control can be managed from the OCC site, including flight termination. All communications are secure as the OCC GSE computers are protected by a firewall and the NDISC and legacy POCC equipment connects to the outside world via NASAÕs Closed IP Operational Network (IONet). During an LDB flight, operators are on duty 24 hours a day. A large UPS and a generator protect the OCC building power.
0273-1177/$30 Ó 2004 COSPAR. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.asr.2003.07.035
1624
S. Breeding, B. Stilwell / Advances in Space Research 33 (2004) 1623–1626
Fig. 1. Basic LDB flight communications scheme.
3. OCC and ROCC site computer hardware Each of the four OCC GSE computers have a single board computer with dual, 500 MHz Pentium III processors, 384 Megabytes of SDRAM, a 16 serial port Digiboard, a 10/100 network card, a 21 inch flat screen monitor, 9 Gigabyte removable hard disk drive and a read/write CD drive. The operating system is Windows 2000. The ROCC computer hardware is identical, with the exception that the monitor is only 17 inches. The main and backup NDISC computers are very similar. They have no Digiboard, they share a single 17-inch monitor, their hard drive is only 4 Gigabytes, and they have a DAT40 tape drive rather than a read/write CD drive.
4. OCC and ROCC site computer software All NSBF software for the OCC and NDSIC computers is written with National InstrumentsÕ LabVIEW
graphical programming language. LabVIEW is a high level language. It is well supported, easy to learn, and it is a good fit for the electrical engineering mind set. It has a feel very similar to drag and drop schematic capture programs. Engineers with experience with these hardware tools tend to find LabVIEW easy to use and familiar. 4.1. OCC/ROCC GSE computer software The NSBF OCC/ROCC software is modular and configurable. Configuration information is stored in an initialization file which is accessed at startup to define which modules are loaded, port assignments, addresses, etc. The operator can also make configuration changes interactively. As changes are made the initialization file is updated, insuring that the file always reflects the current configuration. If the software should ever need to be restarted, it will be configured the same as it was before the restart. The software design makes liberal use
S. Breeding, B. Stilwell / Advances in Space Research 33 (2004) 1623–1626
of state machines. These are easy to understand and tend to be very deterministic. Thus the software is stable and reliable. The modular approach keeps the software efficient. Unneeded modules are not even loaded. For example, at the OCC there is typically not a LOS radio link but the TDRSS link is vital. Thus, the LOS command and data modules are not loaded on the OCC machines while the TDRSS command and data modules are loaded and run. At the ROCC machine there is no TDRSS link, but the LOS links are vital. In this case, the TDRSS command and data modules are not loaded, while the LOS modules are loaded and run. A very powerful tool of the OCC/ROCC software is the client/server capability mentioned earlier. For example, it is common for the balloon to fly out of line of sight range from the ROCC site a few days after launch. Typically, the OCC computer continues to communicate with the payload via a TDRSS link. In this case, the OCC computer is configured as a server and the ROCC is configured as a client. The ROCC then receives housekeeping data updates periodically (usually every 30 s) from the OCC computer. Thus, the operations personnel at the ROCC can monitor flight details even when their communication links with the payload are no longer effective. The operator interface for the OCC/ROCC software is designed to quickly inform the operator of problems or potential problems. The various information screens use color-coded displays to indicate acceptable (green), caution (yellow), or warning (red) states of specific parameters. The level definitions are configurable via setup files, so they can be changed with different flights. 4.2. NDISC computer software The NDISC computer software is a fairly new tool at NSBF. It is designed to interface with WDISC (WSC data interface service capability) in White Sands. The NDISC machine and its software are designed to support up to four simultaneous flights. The software is not as modular as the OCC/ROCC software as the tasks are not as configurable. The main configurable portions of the NDISC system are modules dealing with specific flights. For example, if only one flight is active then only one set of TCP-IP link support modules are loaded and run. If all four flights are active then four sets of link support modules are loaded and run. The main run screen of the NDISC software is very simple and easy to understand. Color-coded icons tell the operator when specific forward and return links are active (green) or inactive (red). If a link failure occurs it is a very simple step for the operator to click on a single button to fail over to the backup links.
1625
5. Science interface details See Fig. 2 for a simplified look at science communications for LDB flights. The science OCC computer, located in the lower left portion of Fig. 2 , is connected to the NSBF OCC computer via two serial ports. One is a 2400-baud command connection. The science computer issues commands to and receives command responses from the OCC computer on this serial port. The second serial connection is a 19200-baud data input only connection from the OCC computer. The OCC computer writes high rate and low rate data, as well as low rate information from the optional science stack out this port. Both of these ports are simple, three-wire connections (no flow control, just transmit, receive and ground). The science OCC computer is usually unmanned, so it is typically connected to the Internet via a firewall. The science OCC computer runs some type of serial interface software to talk with the NSBF OCC computer. The science users connect to the science OCC computer via the Internet to retrieve data, issue commands, etc. The NSBF OCC computer is the primary operator interface for flight control. The operator uses it to check flight status, issue commands as needed to the balloon equipment, etc. The NSBF OCC computer sends control commands, and forwards science commands, to the NSBF NDISC computer via a rather complex TCP/IP socket connection. The NSBF OCC computer connects to the Internet via a firewall. Using this Internet connection it routes through the White Sands Complex computers, connecting to the NSBF NDISC computer via NASAÕs Closed IONet. Actually the NSBF OCC computer acts as a server and the NSBF NDISC computer acts as a client, so the NSBF NDSIC computer actually initiates the connection and periodically sends a command request packet to the NSBF OCC computer. The NSBF OCC computer then responds by sending all buffered commands to the NSBF NDISC computer. The NDISC computer forwards the commands to the WDISC computers at WSC for TDRSS transmission. The WDISC computers at WSC receive data from the balloon payload via the TDRSS satellite and forward it to the NSBF NDISC computer via a socket connection across the Closed IONet. The NSBF NDISC computer logs and forwards all TDRSS data received from WSC out an output only serial port at 19200 baud. The NSBF OCC computer receives this data and logs it. It then either forwards it to the science OCC computer (science data) or consumes the data for display or control purposes. The science payload computer located on the balloon gondola connects to the NSBF SIP flight computer via two serial ports. One is an output-only high rate data connection (19200 baud). The other is a bi-directional low rate serial connection (1200 baud). The science
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S. Breeding, B. Stilwell / Advances in Space Research 33 (2004) 1623–1626
Fig. 2. Simplified block diagram – TDRSS/WDISC science communications.
payload computer receives commands from the NSBF SIP flight computer on the low rate port. It also writes low rate data to the NSBF SIP flight computer on this port. The science payload computer writes high rate data to the NSBF SIP flight computer on the outputonly data port. If the science group is using the optional science stack, it communicates with the NSBF SIP flight computer at 4800 baud on a serial party line. The NSBF SIP flight computer receives commands from WSC via the TDRSS satellite and either consumes the commands as flight control functions, or forwards them to the science payload computer (science commands). The NSBF SIP flight computer forwards science data and NSBF SIP housekeeping data to WSC via the TDRSS satellite.
Higher gain results in higher signal-to-noise ratios for the communications signals. This results in a wider bandwidth and faster signals. While it is still being tested, it is hoped that it will allow data rates over 100,000 baud. If this does turn out to be true, then the serial rates for the two high rate data connections in Fig. 2 will increase to at least 115,200 baud. Another possible change might be to completely eliminate the serial data connection between the NSBF NDISC computer and the NSBF OCC computer. The data would be transferred using the already existing command TCP/IP socket connection.
5.1. New high gain TDRSS antenna
The NSBF LDB ground station equipment provides a reliable, versatile, and user-friendly interface to LDB flight payloads. On-going developments at NSBF continue to improve the performance and reliability of long duration balloon flights.
Personnel at Wallops Flight Facility have developed a high-gain TDRSS antenna for balloon flights. This antenna provides 18 dB of gain to the satellite signals.
6. Conclusions