Badr-B

Badr-B (also referred to as Badr-2), is a follow-up of the Pakistani Badr-A microsatellite. It was built in collaboration with European industry and science institutes. SIL (Space Innovations Limited) of Newburry, UK provided the satellite bus, the spacecraft integration was performed by SUPARCO (Pakistan Space and Upper Atmosphere Research Commission), demonstrating the use of relatively inexpensive microsatellite missions in the field of space technology transfer. SUPARCO, with headquarters in Karachi, is the national space agency of Pakistan. Prime objectives of the Badr-B mission are: ^{1) 2)}

• Commencement of an indigenous development capability of low-cost satellites and creation of a needed infrastructure for future development in this field

• Acquisition of know-how in all fields of satellite and instrument design/development.

Background: Badr-A, a microsatellite of 52 kg (an experimental digital communications satellite built by SSTL of Surrey, UK), was launched July 16, 1990 as a secondary payload on a Chinese booster (Long March 2) from Xichang, China, into an elliptical orbit (perigee of 208 km, apogee of 988 km, inclination of 28.5º). The S/C operated until Aug. 21, 1990; it ceased functioning due to an onboard subsystem failure.
Note: "Badr" is the name of a plain in Saudi Arabia (about 120 km from Medina) where the historic "Battle of Badr" took place in 624 AD between Muslims and non-Muslims during the lifetime of the Prophet Muhammad. The Battle of Badr is considered the most important among the Islamic battles of Destiny. The series of Pakistani satellites was named in honor of this event: the first one being Badr-1 (or Badr-A) and the second one Badr-B.

Spacecraft:

Badr-B is a gravity-gradient stabilized small Earth Observation satellite (the S/C is spin-stabilized prior to boom deployment). The S/C bus structure is polyhedral in shape fabricated from aluminum alloy (T6061). The bus has a size of 51 cm x 51 cm x 46.5 cm. Most subsystems are mounted onto a central shelf, which is attached to a thrust tube; its base contains a strong-ring, forming part of the separation system. The deployed boom has a length of 6 m, it is mounted within the trust tube and deploys through the strong-ring. The Earth-pointing face of the S/C accommodates the communication antennas (VHF, UHF, and S-band), the magnetometer, and the CCD camera. S/C power is provided with GaAs solar panels mounted on the external surface of the S/C bus. Attitude sensing is provided by a pair of two-axis digital sun sensors and by a three-axis fluxgate magnetometer. Actuation is achieved by a pair of magnetorquer rods and by the gravity-gradient boom (4 kg of tip mass). The satellite mass is 68.5 kg, and produces 25 W of average power. The onboard data handling systems are based on dual redundant radiation hardened transputers and microprocessor. The design life of Badr-B is 2 years (with extension goal).

Badr-B was launched on a Zenit-2 launch vehicle from Baikonur, Kazakhstan, as a secondary payload on Dec. 10, 2001. The prime payload on this flight was METEOR-3M-1 of Russia; other secondary payloads were: Compass of IZMIRAN, Moscow, Maroc-Tubsat of Morocco, and REFLECTOR (Russian/US microsatellite).

Orbit: circular sun-synchronous polar orbit, altitude = 1018 km, inclination = 99.64º.

RF communications: S-band telemetry and telecommand, VHF/UHF store-and-forward operations. Badr-B is being tracked and communicated with regularly from the TT&C station at Lahore, Pakistan.

Figure 1: Illustration of the Badr-B spacecraft (image credit: SUPARCO)

Table 1: Overview of communication parameters

Figure 2: Photo of the compact boom trust tube (image credit: SUPARCO)

Figure 3: Photo of the Badr-B satellite with the undeployed boom on top (image credit: SUPARCO)

Sensor complement:

EIC (Earth Imaging Camera), designed and developed at RAL. EIC utilizes a wide-angle CCD array camera with an instrument mass of 2.5 kg. The camera operates at visible wavelengths and uses a large format CCD to achieve 250 m x 250 m resolution on the ground with a field of view of ±8.5º (equivalent to 194 x 144 km on the ground). The challenge in designing and building this instrument has been the need to maintain performance with restrictions on the available space, mass, power and schedule. Snapshot imagery can be provided from any part of the globe, stored onboard and later transmitted to the ground. ³⁾

Figure 4: Illustration of the EIC camera head and the compact electronics control unit (image credit: RAL)

CDE (Compact Dosimeter Experiment). The objective is to measure ionizing radiation levels encountered in polar orbits. The total accumulated dose is measured with miniature RadFET (Radiation-sensitive Field Effect Transistor) sensors based on pMOS technology, installed at various spacecraft locations (total of 8 RadFETs).

Figure 5: Photo of the dosimeters of CDE

S&FE (Store & Forward Experiment). The objective is to provide point-to-point communications for 5-7 users. It consists of a UHF/VHF communications system linked to the onboard computer. The system permits uplinking of encoded information along with recipient address. The information is downlinked when the S/C is in reach of the recipient user location.

Battery End-of-Charge Detector. The objective is to monitor the battery charge status. The technique employed is to monitor the temperature of the battery. It detects a small rise in temperature at the end of the battery charge sequence and acts for overcharge protection.

2) http://www.suparco.gov.pk/sat_badr2.htm

3) http://www.ssd.rl.ac.uk/ssd/ccdtg/BADR-B.htm

This description was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" - comments and corrections to this article are welcomed by the author.