Question: How many missions did NASA's space shuttle program have before ending?
About the article "NASA", section "Space Shuttle program (1972–2011)".

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Space Shuttle "Columbia" (NASA Orbiter Vehicle Designation: OV-102) was the first spaceworthy Space Shuttle in NASA's orbital fleet.
First launched on the STS-1 mission, the first of the Space Shuttle program, it completed 27 missions before disintegrating during re-entry on February 1, 2003 near the end of its 28th mission, STS-107, resulting in the deaths of all crew members aboard. 
NASA's Space Shuttle Program, officially called the Space Transportation System (STS), was the United States government's manned launch vehicle program from 1981 to 2011, with the program officially beginning in 1972.
The winged Space Shuttle orbiter was launched vertically, usually carrying four to seven astronauts (although two and eight have been carried) and up to 50,000 lb (22,700 kg) of payload into low Earth orbit (LEO).
When its mission was complete, the Shuttle could independently move itself out of orbit using its Orbital Maneuvering System (it oriented itself heads down and tail first, firing its OMS engines, thus slowing it down) and re-enter the Earth's atmosphere.
During descent and landing the orbiter acted as a re-entry vehicle and a glider, using its RCS system and flight control surfaces to maintain altitude until it made an unpowered landing at either Kennedy Space Center or Edwards Air Force Base.
The Shuttle is the only winged manned spacecraft to have achieved orbit and land, and the only reusable manned space vehicle that has ever made multiple flights into orbit (the Russian shuttle Buran was very similar and had the same capabilities but made only one unmanned spaceflight before it was cancelled).
Its missions involved carrying large payloads to various orbits (including segments to be added to the International Space Station), providing crew rotation for the International Space Station, and performing service missions.
The orbiter also recovered satellites and other payloads (e.g.
from the ISS) from orbit and returned them to Earth, though its use in this capacity was rare.
Each vehicle was designed with a projected lifespan of 100 launches, or 10 years' operational life, though original selling points on the shuttles were over 150 launches and over a 15 year operational span with a 'launch per month' expected at the peak of the program, but that never did happen.
The program formally commenced in 1972, although the concept had been explored since the late 1960s, and was the sole focus of NASA's manned operations after the final Apollo and Skylab flights in the mid-1970s.
The Shuttle was originally conceived of and presented to the public in 1972 as a 'Space Truck' which would, among other things, be used to build a United States space station in low Earth orbit during the 1980s and then be replaced by a new vehicle by the early 1990s.
When the concept of the U.S. space station evolved into that of the International Space Station, which suffered from long delays and design changes before it could be completed, the service life of the Space Shuttle was extended several times until 2011 when it was finally retired — serving at least 15 years longer than it was originally designed to do.
In 2004, according to the President George W. Bush's Vision for Space Exploration, use of the Space Shuttle was to be focused almost exclusively on completing assembly of the ISS, which was far behind schedule at that point.
The first experimental orbiter "Enterprise" was a high-altitude glider, launched from the back of a specially modified Boeing 747, only for initial atmospheric landing tests (ALT).
Enterprise's first test flight was on February 18, 1977; leading to the launch of the first space-worthy shuttle "Columbia" on April 12, 1981 on STS-1.
The Space Shuttle program finished with its last mission, STS-135 flown by "Atlantis", in July 2011, retiring the final Shuttle in the fleet.
The Space Shuttle program formally ended on August 31, 2011.
Retirement of the Shuttle ended the era in which all of America's varied space activities were performed by one craft -or even one organization.
Functions performed by the Shuttle for 30 years will be done by not one but many different spacecraft currently flying or in advanced development.
Secret military missions are being flown by the US Air Force's "highly successful" unmanned mini-space plane, the X-37B.
By 2012, cargo supply to the International Space Station began to be flown by privately owned commercial craft under NASA's Commercial Resupply Services by SpaceX's successfully tested and partially reusable Dragon spacecraft, followed by Orbital Sciences' Cygnus spacecraft in late 2013.
Crew service to the ISS will be flown exclusively by the Russian Soyuz while NASA works on the Commercial Crew Development program.
For missions beyond low Earth orbit, NASA is building the Space Launch System and the Orion spacecraft. 
"Space Transportation System" (NASA's formal name for the overall Shuttle program) was created to transport crewmembers and payloads into low Earth orbits.
It would afford the opportunity to conduct science experiments on board the shuttle to be used to study the effects of space flight on humans, animals and plants.
Other experiments would study how things can be manufactured in space.
The shuttle would also enable astronauts to launch satellites from the shuttle and even repair satellites already out in space.
The Shuttle was also intended for research into the human response to zero-g.
The Shuttle was originally billed as a space vehicle that would be able to launch once a week and give low launch costs through amortization.
Development costs were expected to be recouped through frequent access to space.
These claims were made in an effort to obtain budgetary funding from the United States Congress.
Beginning in 1981, the space shuttle began to be used for space travel.
However, by the mid-1980s the concept of flying that many shuttle missions proved unrealistic and scheduled launch expectations were reduced 50%.
Following the "Challenger" accident in 1986, missions were halted pending safety review.
This hiatus became lengthy and ultimately lasted almost three years as arguments over funding and the safety of the program continued.
Eventually the military resumed the use of expendable launch vehicles instead.
Missions were put on hold again after the loss of "Columbia" in 2003.
Overall, 135 missions were launched during the 30 years after the first orbital flight of "Columbia", averaging approximately one every 3 months. 
The retirement of NASA's Space Shuttle fleet took place from March to July 2011.
"Discovery" was the first of the three active space shuttles to be retired, completing its final mission on March 9, 2011; "Space Shuttle Endeavour" did so on June 1.
The final shuttle mission was completed with the landing of "Atlantis" on July 21, 2011, bringing about the end of the 30-year Space Shuttle program.
The Shuttle was originally conceived of and presented to the public in 1972 as a 'Space Truck' which would, among other things, be used to build a United States space station in low earth orbit in the early-1990s and then be replaced by a new vehicle.
When the concept of the U.S. space station evolved into that of the International Space Station, which suffered from long delays and design changes before it could be completed, the service life of the Space Shuttle was extended several times until 2011 when it was finally retired.
In 2010 the Shuttle was formally scheduled for retirement with "Atlantis" being taken out of service first after STS-132 in May of that year, but the program was once again extended when the two final planned missions were delayed until 2011.
Later, one additional mission was added for "Atlantis" for July 2011, extending the program further.
Counter-proposals to the shuttle's retirement were considered by Congress and the prime contractor United Space Alliance as late as spring 2010.
Hardware developed for the Space Shuttle met various ends with conclusion of the program, including donation, disuse and/or disposal, or reuse.
An example of reuse, is that one of the three Multi-Purpose Logistics Module (MPLM) was converted to a permanent module for the International Space Station. 
From 1964, Lind worked at the NASA Goddard Space Flight Center as a space physicist.
He was involved in experiments to determine the nature and properties of low-energy particles within the Earth's magnetosphere and interplanetary space.
Lind applied for NASA's third group of astronauts but did not have enough flight hours, and was too old for the fourth group.
After the age restriction changed, he was among the fifth group, the "Original Nineteen", selected in April 1966.
Although pilots comprised the Original Nineteen (unlike the fourth and sixth groups, which included only scientists), Deke Slayton assigned Lind to science-related tasks due to his doctorate.
For the Apollo program he helped to develop the tools used on the lunar surface, and was a possible crewman of one of the canceled missions.
Lind served as backup pilot for Skylab 3 and Skylab 4, the second and third manned Skylab missions; was on standby for a rescue mission planned when malfunctions developed on Skylab 3; and was a possible crewman of Skylab B.
When the Smithsonian Air and Space Museum received the unused Skylab B he "cried ceremonially in front of it", Lind later said; "I was ... in the right place at the wrong time".
For the shuttle program Lind was also a member of the Astronaut Office's Operations Missions development group, responsible for developing payloads for the early Space Shuttle Orbital Flight Test (OFT) missions, and the Canadarm.
He finally flew as a Mission Specialist on STS-51-B (April 29 to May 6, 1985), logging over 168 hours in space.
Lind waited longer than any other American for his first spaceflight, 19 years.
16 members of the Original Nineteen, as well as 14 in later astronaut groups, flew in space before him.
Lind left NASA in 1986 and for nine years served as a professor of physics and astronomy at Utah State University.