Question: Which spacecraft out of the Kepler, Hershel and Planck spacecrafts was the most expensive to build? Passage 1:Yahya bin Hamza was a member of the Zaidi elite, but not of the dynasty of the Rassids that usually provided imams. He was a 13th-generation descendant of imam Ali ar-Ridha (d. 818). The old Yemeni imam al-Mahdi Muhammad bin al-Mutahhar had conquered large highland territories from the Rasulid Dynasty, including the commercially and politically important city San'a. After his demise in 1328, no less than four claimants for the imamate surfaced. Apart from Yahya, these included an-Nasir Ali bin Salah, Ahmad bin Ali al-Fathi, and the deceased imam's son al-Wathiq al-Mutahhar. Yahya emerged as the supreme figure and quickly secured San'a. With the city as his base, he waged war in the following years against Taiyabi Ismaili groups of the Hamdan tribe in the Wadi Dahr. The Rasulids were in no position to take back their lost lands in the Yemeni highland, leaving the Zaidi positions unthreatened. The imam was a prominent scholar who authored Al-Intisar, the most comprehensive Zaydiyyah law book, and Ad-Da'wa al-amma, a work encouraging struggle for the true faith. It was popularly said that the number of pages he wrote were equal to the days he lived. Al-Mu'ayyad Yahya died in 1346 (or, in another account, 1349), and was buried in Dhamar. On his death, San'a was seized by two Zaidi brothers, Ibrahim bin Abdallah and Da'ud bin Abdallah, who ruled as emirs and did not claim the imam title. Their family would control San'a until 1381.
 Passage 2:Although no planetary probes were launched in 2009, four astronomical observatories were placed into orbit. The Kepler spacecraft, which was launched by a Delta II on 7 March, entered an Earth-trailing heliocentric orbit from where it will search for exoplanets. On 14 May, and Ariane 5ECA launched the Herschel and Planck spacecraft. Both were placed at the L Lagrangian point between the Earth and Sun, from where they will be used for astronomy. Herschel carries an infrared telescope whilst Planck carries an optical one. The fourth observatory to be launched was the Wide-field Infrared Survey Explorer, or WISE, which is a replacement for the Wide Field Infrared Explorer which failed shortly after launch. WISE was launched into a sun-synchronous orbit by a Delta II on 14 December, and will be used for infrared astronomy. Repairs made to the Hubble Space Telescope during STS-125 restored it to full operations after a series of malfunctions in 2008.
 Passage 3:He has been active in industry, making significant contributions as a key designer and developer of projects such as IBM's VM/370 operating system and Lockheed's DIALOG information retrieval system. He has served as a consultant to many major corporations, such as IBM, AT&T, and Citicorp. He has also been the founder or co-founder of several high-tech firms, including Intercomp (acquired by Logicon), Mitrol (acquired by General Electric's Information Systems Company), Cambridge Institute for Information Systems, founded with John J. Donovan (its successor corporation was named Cambridge Technology Group, founded by John J. Donovan), iAggregate (acquired by ArsDigita, which was subsequently acquired by Red Hat), and now operates a hotel in the 14th century Langley Castle in England. Madnick is involved with the research effort at BMLL Technologies, a Cambridge spin-off working in the field of machine learning on the limit order book.

Output: 2