CubeSat - Launch 2
CubeSat - Launch 2
The second multiple spacecraft launch, involving 3 CubeSats (UWE-1, XI-V, and NCube-2), was released/deployed from SSETI-Express (Student Space Education and Technology Initiative), a microsatellite of European students, and itself a secondary payload on a multiple spacecraft mission. 1)
Launch: The launch of this multiple S/C mission took place on Oct. 27, 2005 (Cosmos-3M launch vehicle of AKO Polyot from the Plesetsk Cosmodrome, Russia) involving the following spacecraft:
• TopSat of QinetiQ (UK), and China-DMC+4 (Beijing-1) of SSTL (UK) as primary payloads.
• The other secondary payloads on this multi-satellite flight were: SSETI Express (European Students), Mozhayets 5 (Russia), Sinah-1 (Iran), and Rubin-5 (OHB, Bremen, Germany).
CubeSat deployment. The three CubeSat passengers of SSETI-Express (i.e., picosatellites) were: UWE-1 (Universität Würzburg Experimentalsatellit-1), Würzburg, Germany; XI-V (X-factor Investigator-V) of the University of Tokyo, Tokyo, Japan; and NCube-2 (Norwegian CubeSat-2) from Norway.
The deployment of the CubeSats employed the T-POD (Tokyo-Picosatellite Orbital Deployer) system, provided jointly by Japan (University of Tokyo) and Canada (University of Toronto); one T-POD is being used for each CubeSat. 2) 3) 4)
Note: T-POD was already developed and used to eject the XI-IV CubeSat from the Rockot launch vehicle in a multiple CubeSat launch (6 picosatellites) on June 30, 2003 from Plesetsk, Russia. The T-POD development is not regarded as a competition to P-POD (Poly-Picosatellite Orbital Deployer) of CalPoly; rather, it is considered a complementary element in case of need being offered by a potential launch opportunity.
Figure 1: Illustration of T-POD and the CubeSats (image credit: TU Wien)
Deployment status: The 3 CubeSats (UWE-1, XI-V and NCube-2) were deployed successfully from SSETI Express 64 minutes into the mission and so far signals from XI-V and UWE-1 have been successfully received at their respective ground stations. However, during the initial mission days, no signals of NCube-2 could be received.
Orbit: Sun-synchronous circular orbit of all spacecraft, altitude = 686 km, inclination = 98º, LTAN (Local Time on Ascending Node)) at 10:30 hours.
UWE-1 (Universität Würzburg's Experimentalsatellit-1)
UWE is a picosatellite technology project within the CubeSat family standard, developed and built by students of the University of Würzburg and Fachhochschule Weingarten, Germany. The intent is always to enrich the student training program, to stimulate interest in a problem-solving multi-disciplinary technical environment, to be imaginative and resourceful, and to take some risks – with ample and essential help from mentors and partners (industry, institutional, or otherwise).
The overall project objective is to test adaptations of Internet protocols [such as: TCP (Transmission Control Protocol), UDP (User Datagram Protocol), SCTP (Stream Control Transmission Protocol), HTTP (HyperText Transfer Protocol)] to the space environment, characterized by significant signal propagation delays due to the large distances and much higher noise levels compared to terrestrial links. 5) 6) 7) 8) 9)
Figure 2: Illustration of the UWE-1 spacecraft and its elements (image credit: University of Würzburg)
UWE-1 is a CubeSat of size 10 cm x 10 cm x 10 cm with a mass of =< 1.0 kg, designed and developed by an international team of students. The structural design of the satellite satisfies the CubeSat requirements with regard to size, mass and strength (launch phase). The picosatellite is comprised of the subsystems: onboard data handling, communication, power, orbit and attitude control, structure, and thermal. The attitude of the satellite is passively controlled by means of permanent magnets (in two axis). The axis of “no magnet control” is selected as the spin axis of the satellite. The power subsystem uses surface-mounted solar cells (triple-junction GaAs cells) providing an average power of 2 W, sufficient for spacecraft operations and battery recharging (use of 2 Li-ion batteries, each with a capacity of 2300 mAh).
Figure 3: Block diagram of the power subsystem (image credit: University of Würzburg)
A micro Linux operating system (µCLinux) is implemented in a low-power H8S-2674R microprocessor (Hitachi) to provide the capability of testing the communication protocols and to increase the potential for applications, such as ftp-server, http-server, or mission-specific applications. The onboard software can be upgraded and modified to suit the operational requirements of the application on the spaceborne platform. The onboard communication between the Linux operating system and the transceiver utilizes the 6Pack protocol.
Figure 4: Overview of the OBDH subsystem (image credit: University of Würzburg)
The OBDH subsystem is built around the 16 bit H8S 2674 microprocessor. Under normal conditions, the complete OBDH system requires typically less than 300 mW, a significant benefit of this architecture. Several interfaces connect the main processor to the various on–board components. A connection to the power bus supplies the board with energy, a control bus to the power board offers the possibility to implement in software an efficient power management based on sensor information, one I2C interface is used to read data from the onboard sensors, and an RS-232 interface to the transceiver is used to send and receive data from the ground station.
RF communications: A modified off-the-shelf transceiver (1 W transmit power) is being used to communicate with the ground station in the radio-amateur band (UHF, VHF) using the AX-25 protocol (assigned downlink frequency of 437.505 MHz). The transmission rate and modulation can be modified by command, to either a 9600 baud FSK or to a 1200 baud AFSK-modulated signal. The ground station for UWE-1 (at the University of Würzburg) has the capability of sending and receiving on the amateur radio band. UWE-1 provides services like ftp or a web server. These services can be accessed directly from the Internet due to the configuration of the ground station as a gateway between the Internet and the satellite. All applications running onboard UWE-1 can also be accessed via the Internet.
Figure 5: Photo of the UWE-1 spacecraft (image credit: University of Würzburg)
Figure 6: Integrated modem and transceiver with RS-232 interface (image credit: University of Würzburg)
Mission status: UWE-1 is being operated by a student team at the University of Würzburg using their ground station on campus (the team is also being supported by downlink receptions from amateur radio operators throughout the world).
The spacecraft was operating nominally in 2006. However, since June 2006, no communication signals can be received from UWE-1, resulting in a number of investigations as to the causes of this failure.
The main mission objective of UWE-1 is to analyze and optimize different implementations of Internet protocols in space (TCP, UDP, SCTP, etc.), taking into account typical characteristics of the radio link regarding delays, noise, interruptions, low bandwidth and high packet loss rates. The complete payload is implemented in software and a comparison basis for performance measurements had to be established.
Since the µCLinux operating system employs the standard TCP/IP protocol stack by default, this is being used as a comparison basis for performance measurements of the various protocol experiments.
XI-V (X-factor Investigator-V) CubeSat
The XI-V CubeSat of ISSL (Intelligent Space Systems Laboratory) at the University of Tokyo (UT) is a follow-on mission to XI-IV launched June 30, 2003 and still operational as of 2006. Originally, XI-V was developed as a backup and a hardware simulator of XI-IV. Now, XI-V is being used as an upgraded CubeSat with the same basic design as XI-IV. The solar cells produce an average power of 1.1W. A Li-ion battery is used with a capacity of 6.2 Ah. Attitude control is provided by a passive permanent magnet (1300 mT) and hysteresis dampers. 10) 11) 12) 13)
RF communications: Onboard data storage of up to 64 kbyte. A standard Tx-TNC (Terminal Node Controller) PIC16C622 is used with 128 byte of cache memory. Antenna: monopole (uplink), dipole (downlink).
• The downlink frequency is 437.490 MHz (UHF), FSK modulation, AX.25 protocol, data rate of 1.2 kbit/s, RF output power of 1 W. In addition there is a beacon at 436.8475 MHz, CW (Continuous Wave), 80 mW.
• The uplink employs a Rx-TNC, PIC16C711, the frequency is in VHF, FSK modulation, AX.25 protocol, data rate of 1.2 kbit/s.
The S/C is being operated by the UT amateur (Ham) radio station (6-7 passes per day). In addition, any worldwide amateur radio station is capable of telemetry data reception.
Figure 7: Photo of the XI-V CubeSat with stowed antennas in launch configuration (image credit: ISSL)
The objective of the XI-V mission is to demonstrate new space technologies.
1) Demonstration of CIGS [Cu(In,Ga)Se2] thin-film solar cells in orbit, developed by JAXA (Japan Aerospace Exploration Agency).
The newly designed cells are considered to be much more tolerant toward space radiation effects. The CubeSat XI-V is collecting data to verify the long-term radiation-hardness of the CIGS solar cells. In addition, GaAs solar cells are being tested on XI-V to be used on the future PRISM mission of ISSL.
Figure 8: CIGS solar cell mounted on XI-V (image credit: ISSL)
Table 1: Specifications of the solar cells on XI-V
Figure 9: Various types of solar cells mounted on the XI-V CubeSat (image credit: ISSL)
2) Improvement of camera control software.
XI-V carries the same CMOS camera as flown on XI-IV; however, with a considerably improved control software. A major improvement is the image pixel size in the downlink; it used to be 128 x 120 pixels for CMOS on XI-IV, and is now enlarged to 320 x 240 pixels corresponding to QVGA (Quarter Video Graphics Array) size. The improved message transmission service is via a Morse-coded CW signal and FM packet (1200 baud). The messages can be received from all over the world (they are being collected from the public and uploaded to the satellite).
3) Improvement of image observations.
The CMOS camera features a continuous shooting mode capable of taking eight continuous images with a minimum interval of 200 ms. This mode is being used in the analysis to estimate the attitude motion of the spacecraft in conjunction with the current of the solar cells on the six surface of the satellite. - Also, the CMOS camera is equipped with an ND (Neutral Density) filter at the tip of the lens module to reduce the amount of light coming into the CMOS camera (avoidance of saturation).
The XI-V payload consists of a CMOS color camera for experimenting in imaging technology. The detector has a physical size of about 0.8 cm x 0.8 cm and contains 644 x 484 pixels in the visible spectrum. The lens has a focal length of 6 mm, f/1.8. The FOV is about 35º x 35º, each image covers a ground area of about 400 km x 400 km from orbital altitude with a spatial resolution of about 3-4 km. The source data is available as 16 bit RGB output. Some onboard preprocessing is performed for data volume reduction (15,360 pixels per image). An image in the downlink contains now 320 x 240 pixels. The camera has a mass of 20 gram with a power consumption of 120 mW. 14)
Table 2: Specification of images taken by the CMOS camera on XI-IV and XI-V
With XI-V, ISSL has its second CubeSat in orbit. The planned technology demonstrations were conducted. The spacecraft operated for five years and five months on orbit.
• Earth imaging mission: More than 250 images were taken by the CMOS camera; 80 images were downlinked for six months in its orbit. In addition, it has been confirmed that most camera functions in Table 2 work well. For example, a group of images by continuous shot mode provides some attitude information of the S/C.
• Precise measurement circuit: A notable feature of XI-V is the improvement of the precision of the A/D conversion. The newly designed circuit provides a precise evaluation of the sensor data, essential for its primary mission, namely solar cell evaluation. Up to now, all six cells on XI-V have been confirmed to generate the expected amount of power on orbit.
• The message service mission for the public is being supported. XI-V has the function of transmitting the message stored on its ROM via a Morse-coded CW signal. The messages to be transmitted from all over the world and can be uplinked to the satellite to modify the messages on the ROM.
NCube-2 (Norwegian CubeSat-2)
NCube is a collaborative student picosatellite project (within the framework of CubeSat standards) of four Norwegian universities and educational institutes; these are: Narvik University College (HIN), Norwegian University of Science and Technology (NTNU), Trondheim, Agricultural University of Norway (NLH), and the University of Oslo. The project started in 2001, initiated by the Andøya Rocket Range and the Norwegian Space Center.
NCube-1 is the first picosatellite in the series. As of Nov. 2005, it is awaiting launch on a Dnepr launcher from the Baikonur, Kazakhstan (multi-spacecraft launch involving 12 other CubeSats besides NCube-1).
The overall mission objective of NCube-2 is the same as that of NCube-1 -- namely 1) to demonstrate ship traffic surveillance from a spaceborne platform (LEO satellite), using the maritime AIS (Automatic Identification System) communication concept, introduced by IMO (International Maritime Organization) in 2002, and 2) to use AIS also for animal tracking (movement of reindeer herds).
The NCube-2 satellite conforms to the CubeSat standards in size and mass (1 kg limit). The S/C structure uses a Al 6061 T6 box design. The satellite is three-axis stabilized, employing the activation techniques of magnetic coils and gravity gradient stabilization (the deployable boom has a length of 1.5 m). Attitude sensing of ADCS (Attitude and Control Subsystem) is based on magnetic field measurements (Honeywell HMR2300 digital three-axis magnetometer) and on an analysis of solar cell lighting conditions. Surface-mounted solar panels (on 5 sides) provide power, using monocrystalline solar cells that are manufactured by Institute for Energy Technology (IFE), Norway. A Li-ion battery is used during eclipse phases of the orbit. The EPS (Electric Power Subsystem) is equipped with its own microcontroller which is able to autonomously power subsystems in a predetermined prioritized order.
Figure 10: Photo of the NCube-2 CubeSat (image credit: NTNU)
RF communications: Two deployable VHF/UHF monopole antennas, the S-band antenna, and the boom are mounted on the nadir face of NCube (the boom also serves as VHF antenna). The TNC provides the communications interface to the VHF receiver and the UHF and S-band transmitters. Use of standard amateur radio protocols (AX.25), VHF (144-146 MHz uplink) and UHF (432-438 MHz downlink) frequencies; at data rates of either 1200 or 9600 bit/s. The S-band transmitter is used for payload data transmission.
After a successful launch of SSETI-Express and deployment of NCube-2, the ground stations in Narvik and at Svalbard have not received any confirmed signal from Ncube-2, two weeks into the mission. With no reports from radio amateurs establishing contact either, it seems that the satellite is not sending any signals or is somehow prevented to do so.
After a thorough analyses it is believed that the CubeSat was stuck inside the deployment mechanism.
Experiment/payload: (EKF, AIS)
EKF (Extended Kalman Filter)
AIS (Automatic Identification System)
AIS is a ground based ship-tracking system. The objective is to demonstrate this technology from space. On NCube-2, AIS is also being used to track reindeer herds in the Filefjell mountains. For this purpose, a special reindeer collar was designed by a group of students at the Norwegian University of Life Sciences (UMB) formerly NLH.
Figure 11: Illustration of the reindeer collar tracking device (image credit: UMB)
1) “The History behind SSETI Express,” URL: http://paginas.fe.up.pt/ssetiexpress/history6_en.html
3) “UTIAS/SFL NanoSatellite Ejection System Successfully Demonstrated in Space,” Nov. 7, 2005, URL: http://www.utias-sfl.net/RecentNews/news-20051107.html
4) “Nanosatellite Launch Service,” UTIAS/SFL, URL: http://www.utias-sfl.net/SpecialProjects/LaunchIndex.html
5) R. Barza, Y. Aoki, K. Schilling, “UWE-1, A Student Built Pico-Satellite,” REM-2005 (6th International Workshop on Research and Education in Mechatronics), June 30-July 1, 2005, Annecy, France
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8) B. Herbst, F. Zeiger, M. Schmidt, K. Schilling, “UWE-1: A Picosatellite to Test Communication Protocols,” Proceedings of the 56th IAC 2005, Fukuoda, Japan, Oct. 17-21, 2005, IAC-05-B5.6.A.11
9) Marco Schmidt, “Picosatellite activities of the University of Würzburg,” URL: http://park.itc.u-tokyo.ac.jp/nsat/NS1/files/10th.AM/Presentation_Marco-Schmidt.pdf
11) R. Funase, E. Takei, Y. Nakamura, M. Nagai, A. Enokuchi, C. Yuliang, K. Nakada, Y. Nojiri, F. Sasaki, T. Funane, T. Eishima, S. Nakasuka, “Technology Demonstration on University of Tokyo's Picosatellite `XI-V' and its effective Operations Result using Ground Station Network,” Proceedings of the 56th IAC 2005, Fukuoda, Japan, Oct. 17-21, 2005, IAC-05-B5.3/B5.5.02
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14) Information provided by Nobutada Sako of ISSL, University of Tokyo
15) B. O. Sunde, J. T. Gravdahl, “Attitude Determination for the Student Satellite nCubeII: Kalman Filter,” Proceedings of the 56th IAC 2005, Fukuoda, Japan, Oct. 17-21, 2005, IAC-05-C1.P.04
16) Å.-R Riise,.B. Samuelsen, N. Sokolova, E. T. Sæther, J. Otterstad, E. Eide, et al.,“ncube: The First Norwegian Student Satellite” Proceedings of 17th Annual AIAA/USU Conference on Small Satellites, Logan, UT, Aug. 11-14, 2003
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates.