A reflecting telescope is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century, by Isaac Newton, as an alternative to the refracting telescope which, at that time, was a design that suffered from severe chromatic aberration. Although reflecting telescopes produce other types of optical aberrations, it is a design that allows for large diameter objectives. All of the major telescopes used in astronomy research are reflectors. Reflecting telescopes come in many design variations and may employ extra optical elements to improve image quality or place the image in a mechanically advantageous position. Since reflecting telescopes use mirrors, the design is sometimes referred to as a "catoptric" telescope; the idea that curved mirrors behave like lenses dates back at least to Alhazen's 11th century treatise on optics, works, disseminated in Latin translations in early modern Europe. Soon after the invention of the refracting telescope, Giovanni Francesco Sagredo, others, spurred on by their knowledge of the principles of curved mirrors, discussed the idea of building a telescope using a mirror as the image forming objective.
There were reports that the Bolognese Cesare Caravaggi had constructed one around 1626 and the Italian professor Niccolò Zucchi, in a work, wrote that he had experimented with a concave bronze mirror in 1616, but said it did not produce a satisfactory image. The potential advantages of using parabolic mirrors reduction of spherical aberration with no chromatic aberration, led to many proposed designs for reflecting telescopes; the most notable being James Gregory, who published an innovative design for a ‘reflecting’ telescope in 1663. It would be ten years, before the experimental scientist Robert Hooke was able to build this type of telescope, which became known as the Gregorian telescope. Isaac Newton has been credited with building the first reflecting telescope in 1668, it used a spherically ground metal primary mirror and a small diagonal mirror in an optical configuration that has come to be known as the Newtonian telescope. Despite the theoretical advantages of the reflector design, the difficulty of construction and the poor performance of the speculum metal mirrors being used at the time meant it took over 100 years for them to become popular.
Many of the advances in reflecting telescopes included the perfection of parabolic mirror fabrication in the 18th century, silver coated glass mirrors in the 19th century, long-lasting aluminum coatings in the 20th century, segmented mirrors to allow larger diameters, active optics to compensate for gravitational deformation. A mid-20th century innovation was catadioptric telescopes such as the Schmidt camera, which use both a spherical mirror and a lens as primary optical elements used for wide-field imaging without spherical aberration; the late 20th century has seen the development of adaptive optics and lucky imaging to overcome the problems of seeing, reflecting telescopes are ubiquitous on space telescopes and many types of spacecraft imaging devices. A curved primary mirror is the reflector telescope's basic optical element that creates an image at the focal plane; the distance from the mirror to the focal plane is called the focal length. Film or a digital sensor may be located here to record the image, or a secondary mirror may be added to modify the optical characteristics and/or redirect the light to film, digital sensors, or an eyepiece for visual observation.
The primary mirror in most modern telescopes is composed of a solid glass cylinder whose front surface has been ground to a spherical or parabolic shape. A thin layer of aluminum is vacuum deposited onto the mirror, forming a reflective first surface mirror; some telescopes use primary mirrors. Molten glass is rotated to make its surface paraboloidal, is kept rotating while it cools and solidifies; the resulting mirror shape approximates a desired paraboloid shape that requires minimal grinding and polishing to reach the exact figure needed. Reflecting telescopes, just like any other optical system, do not produce "perfect" images; the need to image objects at distances up to infinity, view them at different wavelengths of light, along with the requirement to have some way to view the image the primary mirror produces, means there is always some compromise in a reflecting telescope's optical design. Because the primary mirror focuses light to a common point in front of its own reflecting surface all reflecting telescope designs have a secondary mirror, film holder, or detector near that focal point obstructing the light from reaching the primary mirror.
Not only does this cause some reduction in the amount of light the system collects, it causes a loss in contrast in the image due to diffraction effects of the obstruction as well as diffraction spikes caused by most secondary support structures. The use of mirrors avoids chromatic aberration but they produce other types of aberrations. A simple spherical mirror cannot bring light from a distant object to a common focus since the reflection of light rays striking the mirror near its edge do not converge with those that reflect from nearer the center of the mirror, a defect called spherical aberration. To avoid this problem most reflecting telescopes use parabolic shaped mirrors, a shape that can focus all the light to a common focus. Parabolic mirrors work well with objects near the center of the image they produce, but towards the edge of that same field of view they suffer from off axis aberrations: Coma - an aberr
STS-125, or HST-SM4, was the fifth and final space shuttle mission to the Hubble Space Telescope. The launch of the Space Shuttle Atlantis occurred on 11 May 2009 at 2:01 pm EDT. Landing occurred on 24 May with the mission lasting a total of just under 13 days. Space Shuttle Atlantis carried two new instruments to the Hubble Space Telescope, the Cosmic Origins Spectrograph and the Wide Field Camera 3; the mission replaced a Fine Guidance Sensor, six gyroscopes, two battery unit modules to allow the telescope to continue to function at least through 2014. The crew installed new thermal blanket insulating panels to provide improved thermal protection, a soft-capture mechanism that would aid in the safe de-orbiting of the telescope by an unmanned spacecraft at the end of its operational lifespan; the mission carried an IMAX camera with which the crew documented the progress of the mission for the Hubble IMAX movie. The crew of STS-125 included three astronauts. Scott Altman visited Hubble in 2002 as commander of the fourth Hubble servicing mission.
John Grunsfeld, an astronomer, has serviced Hubble twice, performing a total of five spacewalks on STS-103 in 1999 and STS-109. Michael Massimino served with both Altman and Grunsfeld on STS-109, performed two spacewalks to service the telescope. NASA managers and engineers declared the mission a complete success; the completion of all the major objectives, as well as some that were not considered vital, upgraded the Hubble telescope to its most technologically advanced state since its launch nineteen years before and made it more powerful. The upgrades helped Hubble to see deeper into the universe and farther into the past, closer to the time of the Big Bang. STS-125 was the only visit to the Hubble Space Telescope for Atlantis; the mission was the 30th flight of Space Shuttle Atlantis and the first by Atlantis in over 14 years not to visit a space station, the last one being STS-66. The fifth servicing mission to Hubble, HST-SM4, was scheduled to launch in late 2005 or early 2006. On 16 January 2004, then-NASA Administrator Sean O'Keefe canceled the mission, as well as any future missions to Hubble, citing safety constraints imposed by the Columbia Accident Investigation Board.
During the announcement, O'Keefe stated that it was his decision alone, not a recommendation from any other departments. The decision was criticized by the media, the science community, those in NASA. Maryland Senator Barbara Mikulski, a member of the Senate subcommittee that oversees NASA's budget, publicly accused O'Keefe of making a decision outside the transparency process against the wishes of the science community, stated she would work to reverse the decision. In March 2004, Representative Mark Udall introduced a bill to the House of Representatives that requested an independent panel of experts review O'Keefe's decision to cancel the servicing mission. In March 2004, Space Telescope Science Institute Director Stephen Beckwith released the results of the Hubble Ultra-Deep Field survey to the entire science community, which helped show the public how important Hubble was to science; the data showed the deepest images taken by a telescope and revealed 10,000 galaxies, some of which most dated back to when the universe was just five hundred million years old.
With Beckwith when he released the data to the scientific community was Mikulski, who said of the results, "I think it's just amazing... this is why I will continue to stand up for Hubble."Joining Mikulski as an advocate for servicing Hubble was NASA's Chief Scientist, physicist John Grunsfeld, present at the meeting when O'Keefe announced the cancellation of the mission. A veteran astronaut of four shuttle missions, including two Hubble servicing missions, Grunsfeld had devoted years to Hubble, was disappointed when O'Keefe canceled the mission, he considered retiring from NASA, but realized if he stayed, he could continue to advance physics in other ways. Instead, Grunsfeld dedicated himself to finding alternate ways to service the telescope by sending a robot into orbit to do the job; when O'Keefe announced his resignation as Administrator in December 2004, five days after a National Academy of Sciences committee opposed O'Keefe's position regarding servicing Hubble, the media and science community saw hope for the telescope's servicing mission to be reinstated.
O'Keefe's replacement, Michael D. Griffin, took just two months after his appointment to announce that he disagreed with O'Keefe's decision, would consider sending a shuttle to repair Hubble; as an engineer, Griffin had worked on Hubble's construction, respected the discoveries the telescope brought to the science community. He agreed with the National Academy of Sciences that a robotic mission was not feasible, said that in light of the "Return to Flight" changes made following the Columbia accident, a shuttle mission to repair Hubble should be reassessed. After the successes of the Return to Flight STS-114 and STS-121 missions, the lessons learned and improvements made following those missions and engineers worked to formulate a plan that would allow the shuttle to service Hubble, while still adhering to the post-Columbia safety requirements. On 31 October 2006, Griffin announced that the Hubble servicing mission was reinstated, scheduled for 2008, announced the crew that would fly the mission, which included Grunsfeld.
Senator Mikulski expressed her delight at the news, stating "The Hubble telescope has been the greatest telescope since Galileo invented the fi
Mars Reconnaissance Orbiter
Mars Reconnaissance Orbiter is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit. The US$720 million spacecraft was built by Lockheed Martin under the supervision of the Jet Propulsion Laboratory; the mission is managed by the California Institute of Technology, at the JPL, in Pasadena, for the NASA Science Mission Directorate, Washington, D. C, it was launched August 12, 2005, attained Martian orbit on March 10, 2006. In November 2006, after five months of aerobraking, it entered its final science orbit and began its primary science phase; as MRO entered orbit, it joined five other active spacecraft that were either in orbit or on the planet's surface: Mars Global Surveyor, Mars Express, 2001 Mars Odyssey, the two Mars Exploration Rovers. Mars Global Surveyor and the rover Spirit have since ceased to function. Opportunity has remained silent since June 10, 2018, NASA declared its mission complete on February 13, 2019; as of that date, 2001 Mars Odyssey and MRO continue to remain operational.
MRO contains a host of scientific instruments such as cameras and radar, which are used to analyze the landforms, stratigraphy and ice of Mars. It paves the way for future spacecraft by monitoring Mars' daily weather and surface conditions, studying potential landing sites, hosting a new telecommunications system. MRO's telecommunications system will transfer more data back to Earth than all previous interplanetary missions combined, MRO will serve as a capable relay satellite for future missions, it has enough propellant to keep functioning into the 2030s. One of two missions considered for the 2003 Mars launch window, the MRO proposal lost against what became known as the Mars Exploration Rovers; the orbiter mission was rescheduled for launch in 2005, NASA announced its final name, Mars Reconnaissance Orbiter, on October 26, 2000. MRO is modeled after NASA's successful Mars Global Surveyor to conduct surveillance of Mars from orbit. Early specifications of the satellite included a large camera to take high resolution pictures of Mars.
In this regard, James B. Garvin, the Mars exploration program scientist for NASA, proclaimed that MRO would be a "microscope in orbit"; the satellite was to include a visible-near-infrared spectrograph. On October 3, 2001, NASA chose Lockheed Martin as the primary contractor for the spacecraft's fabrication. By the end of 2001 all of the mission's instruments were selected. There were no major setbacks during MRO's construction, the spacecraft was moved to John F. Kennedy Space Center on May 1, 2005 to prepare it for launch. MRO science operations were scheduled to last two Earth years, from November 2006 to November 2008. One of the mission's main goals is to map the Martian landscape with its high-resolution cameras in order to choose landing sites for future surface missions; the MRO played an important role in choosing the landing site of the Phoenix Lander, which explored the Martian Arctic in Green Valley. The initial site chosen by scientists was imaged with the HiRISE camera and found to be littered with boulders.
After analysis with HiRISE and the Mars Odyssey's THEMIS instrument a new site was chosen. Mars Science Laboratory, a maneuverable rover had its landing site inspected; the MRO provided critical navigation data during their landings and acts as a telecommunications relay. MRO is using its onboard scientific equipment to study the Martian climate, weather and geology, to search for signs of liquid water in the polar caps and underground. In addition, MRO was tasked with looking for the remains of the lost Mars Polar Lander and Beagle 2 spacecraft. Beagle 2 was found by the orbiter at the beginning of 2015. After its main science operations are completed, the probe's extended mission is to be the communication and navigation system for landers and rover probes. On August 12, 2005, MRO was launched aboard an Atlas V-401 rocket from Space Launch Complex 41 at Cape Canaveral Air Force Station; the Centaur upper stage of the rocket completed its burns over a fifty-six-minute period and placed MRO into an interplanetary transfer orbit towards Mars.
MRO cruised through interplanetary space for seven and a half months before reaching Mars. While en route most of the scientific instruments and experiments were tested and calibrated. To ensure proper orbital insertion upon reaching Mars, four trajectory correction maneuvers were planned and a fifth emergency maneuver was discussed. However, only three trajectory correction maneuvers were necessary, which saved 60 pounds fuel that would be usable during MRO's extended mission. MRO began orbital insertion by approaching Mars on March 10, 2006, passing above its southern hemisphere at an altitude of 370–400 kilometers. All six of MRO's main engines burned for 27 minutes to slow the probe from 2,900 to 1,900 meters per second; the helium pressurization tank was colder than expected, which reduced the pressure in the fuel tank by about 21 kilopascals. The reduced pressure caused the engine thrust to be diminished by 2%, but MRO automatically compensated by extending the burn time by 33 seconds. Completion of the orbital insertion placed the orbiter in a elliptical polar orbit with a period of 35.5 hours.
Shortly after insertion, the periapsis – the point in the orbit closest to Mars – was 426 km from the surface. The apoapsis – the point in the orbit farthest from Mars – was 44,500 km from the surface. On March
New York Stock Exchange
The New York Stock Exchange is an American stock exchange located at 11 Wall Street, Lower Manhattan, New York City, New York. It is by far the world's largest stock exchange by market capitalization of its listed companies at US$30.1 trillion as of February 2018. The average daily trading value was US$169 billion in 2013; the NYSE trading floor is located at 11 Wall Street and is composed of 21 rooms used for the facilitation of trading. A fifth trading room, located at 30 Broad Street, was closed in February 2007; the main building and the 11 Wall Street building were designated National Historic Landmarks in 1978. The NYSE is owned by Intercontinental Exchange, an American holding company that it lists, it was part of NYSE Euronext, formed by the NYSE's 2007 merger with Euronext. The NYSE has been the subject of several lawsuits regarding fraud or breach of duty and in 2004 was sued by its former CEO for breach of contract and defamation; the earliest recorded organization of securities trading in New York among brokers directly dealing with each other can be traced to the Buttonwood Agreement.
Securities exchange had been intermediated by the auctioneers who conducted more mundane auctions of commodities such as wheat and tobacco. On May 17, 1792 twenty four brokers signed the Buttonwood Agreement which set a floor commission rate charged to clients and bound the signers to give preference to the other signers in securities sales; the earliest securities traded were governmental securities such as War Bonds from the Revolutionary War and First Bank of the United States stock, although Bank of New York stock was a non-governmental security traded in the early days. The Bank of North America along with the First Bank of the United States and the Bank of New York were the first shares traded on the New York Stock Exchange. In 1817 the stockbrokers of New York operating under the Buttonwood Agreement instituted new reforms and reorganized. After sending a delegation to Philadelphia to observe the organization of their board of brokers, restrictions on manipulative trading were adopted as well as formal organs of governance.
After re-forming as the New York Stock and Exchange Board the broker organization began renting out space for securities trading, taking place at the Tontine Coffee House. Several locations were used between 1865, when the present location was adopted; the invention of the electrical telegraph consolidated markets, New York's market rose to dominance over Philadelphia after weathering some market panics better than other alternatives. The Open Board of Stock Brokers was established in 1864 as a competitor to the NYSE. With 354 members, the Open Board of Stock Brokers rivaled the NYSE in membership "because it used a more modern, continuous trading system superior to the NYSE’s twice-daily call sessions." The Open Board of Stock Brokers merged with the NYSE in 1869. Robert Wright of Bloomberg writes that the merger increased the NYSE's members as well as trading volume, as "several dozen regional exchanges were competing with the NYSE for customers. Buyers and dealers all wanted to complete transactions as and cheaply as technologically possible and that meant finding the markets with the most trading, or the greatest liquidity in today’s parlance.
Minimizing competition was essential to keep a large number of orders flowing, the merger helped the NYSE to maintain its reputation for providing superior liquidity." The Civil War stimulated speculative securities trading in New York. By 1869 membership had to be capped, has been sporadically increased since; the latter half of the nineteenth century saw rapid growth in securities trading. Securities trade in the latter nineteenth and early twentieth centuries was prone to panics and crashes. Government regulation of securities trading was seen as necessary, with arguably the most dramatic changes occurring in the 1930s after a major stock market crash precipitated the Great Depression; the Stock Exchange Luncheon Club was situated on the seventh floor from 1898 until its closure in 2006. The main building, located at 18 Broad Street, between the corners of Wall Street and Exchange Place, was designated a National Historic Landmark in 1978, as was the 11 Wall Street building; the NYSE announced its plans to merge with Archipelago on April 21, 2005, in a deal intended to reorganize the NYSE as a publicly traded company.
NYSE's governing board voted to merge with rival Archipelago on December 6, 2005, became a for-profit, public company. It began trading under the name NYSE Group on March 8, 2006. A little over one year on April 4, 2007, the NYSE Group completed its merger with Euronext, the European combined stock market, thus forming NYSE Euronext, the first transatlantic stock exchange. Wall Street is the leading US money center for international financial activities and the foremost US location for the conduct of wholesale financial services. "It comprises a matrix of wholesale financial sectors, financial markets, financial institutions, financial industry firms". The principal sectors are securities industry, commercial banking, asset management, insurance. Prior to the acquisition of NYSE Euronext by the ICE in 2013, Marsh Carter was the Chairman of the NYSE and the CEO was Duncan Niederauer. Presently, the chairman is Jeffrey Sprecher. In 2016, NYSE owner Intercontinental Exchange Inc. earned $419 million in listings-related revenues.
The exchange was closed shortly after the beginning of World War I, but it re-opened on November 28 of that year in order to help the war effort by trading bonds, reopened for stock tradin
Near Infrared Camera and Multi-Object Spectrometer
The Near Infrared Camera and Multi-Object Spectrometer is a scientific instrument for infrared astronomy, installed on the Hubble Space Telescope, operating from 1997 to 1999, from 2002 to 2008. Images produced by NICMOS contain data from the near-infrared part of the light spectrum. NICMOS was conceived and designed by the NICMOS Instrument Definition Team centered at Steward Observatory, University of Arizona, USA. NICMOS is an imager and spectrometer built by Ball Aerospace & Technologies Corp. that allows the HST to observe infrared light, with wavelengths between 0.8 and 2.4 micrometers, providing imaging and slitless spectrophotometric capabilities. NICMOS contains three near-infrared detectors in three optical channels providing high resolution and polarimetric imaging, slitless spectroscopy in 11-, 19-, 52-arcsecond square fields of view; each optical channel contains a 256×256 pixel photodiode array of mercury cadmium telluride infrared detectors bonded to a sapphire substrate, read out in four independent 128×128 quadrants.
NICMOS last worked in 2008, has been replaced by the infrared channel of Wide Field Camera 3 after its installation in 2009. The infrared performance of the Hubble has limitations since it was not designed with infrared performance as an objective. For example, the mirror is kept at a stable and high temperature by heaters. HST is a warm telescope; the IR background flux collected by cooled focal plane IR instruments like NICMOS or WFC3 is dominated, at rather short wavelengths, by telescope thermal emission rather than by zodiacal scattering. NICMOS data show that the telescope background exceeds the zodiacal background at wavelengths longer than λ ≈ 1.6μm, the exact value depending on the pointing on the sky and on the position of the Earth on its orbit. Despite this, the combination of Hubble's mirror and NICMOS offered never-before seen levels of quality in near-infrared performance at that time. Dedicated infrared telescopes like the Infrared Space Observatory were ground-breaking in their own way, but had a smaller primary mirror, were out of service at the time of NICMOS installation because they ran out of coolant.
NICMOS overcame this problem by using a machine chiller like a refrigerator, which allowed it operate for years until it went offline in 2008 NICMOS was installed on Hubble during its second servicing mission in 1997 along with the Space Telescope Imaging Spectrograph, replacing two earlier instruments. NICMOS in turn has been superseded by the Wide Field Camera 3, which has a much larger field of view, reaches as far into the infrared; when conducting infrared measurements, it is necessary to keep the infrared detectors cooled to avoid having infrared interference from the instrument's own thermal emissions. NICMOS contains a cryogenic dewar, that cooled its detectors to about 61 K, optical filters to ~ 105 K, with a block of solid nitrogen ice; when NICMOS was installed in 1997, the dewar flask contained a 230-pound block of nitrogen ice. Due to a thermal short that arose on March 4, 1997, during the instrument commissioning, the dewar ran out of nitrogen coolant sooner than expected in January 1999.
During Hubble Service Mission 3B in 2002, a replacement cooling system comprising a cryocooler, cryogenic circulator, external radiator was installed on the Hubble that now cools NICMOS through a cryogenic neon loop. NICMOS was returned to service soon after SM 3B. A new software upload in September 2008 necessitated a brief shutdown of the NICMOS cooling system. Several attempts to restart the cooling system were unsuccessful due to issues with the cryogenic circulator. After waiting more than six weeks for parts of the instrument to warm up, theorized ice particles to sublimate from the neon circulating loop, the cooler once again failed to restart. An Anomaly Review Board was convened by NASA; the ARB concluded that ice or other solid particle migrated from the dewar to the circulator during the September 2008 restart attempt and that the circulator may be damaged, determined an alternative set of startup parameters. A successful restart at 13:30 EST on 16 December 2008 led to four days of cooler operations followed by another shutdown.
On 1 August 2009, the cooler was restarted again. The circulation flow rate to NICMOS was reduced during this operating period confirming blockage in the circulation loop. Continued operation at reduced flow rates would limit NICMOS science so plans for purging and refilling the circulation system with clean neon gas were developed by NASA; the circulation loop is equipped with an extra neon tank and remotely operated solenoid valves for on-orbit purge-fill operations. As of 2013, these purge-fill operations have not yet been performed. On June 18, 2010, it was announced NICMOS would not be available for science during the latest proposal Cycle 18; as of 2013, a decision as to whether the purge-fill operations will be performed and whether NICMOS will be available for science in the future has not been made. NICMOS is the name of the devices's 256×256-pixel imaging sensor built by Rockwell International Electro-Optical Center. NICMOS was noted for its performance in Near-infrared space astronomy, in particular its ability to see objects through dust.
It was used for about 23 months after it was installed, its life limited by set amount of cryo-coolant, later it was used for several years when a new cyro-cooler was installed in 2002. NICMOS co
Spitzer Space Telescope
The Spitzer Space Telescope the Space Infrared Telescope Facility, is an infrared space telescope launched in 2003 and still operating as of 2019. The planned mission period was to be 2.5 years with a pre-launch expectation that the mission could extend to five or more years until the onboard liquid helium supply was exhausted. This occurred on 15 May 2009. Without liquid helium to cool the telescope to the low temperatures needed to operate, most of the instruments are no longer usable. However, the two shortest-wavelength modules of the IRAC camera are still operable with the same sensitivity as before the cryogen was exhausted, have continued to be used to the present in the Spitzer Warm Mission. All Spitzer data, from both the primary and warm phases, are archived at the Infrared Science Archive. In keeping with NASA tradition, the telescope was renamed after its successful demonstration of operation, on 18 December 2003. Unlike most telescopes that are named after famous deceased astronomers by a board of scientists, the new name for SIRTF was obtained from a contest open to the general public.
The contest led to the telescope being named in honor of astronomer Lyman Spitzer, who had promoted the concept of space telescopes in the 1940s. Spitzer wrote a 1946 report for RAND Corporation describing the advantages of an extraterrestrial observatory and how it could be realized with available or upcoming technology, he has been cited for his pioneering contributions to rocketry and astronomy, as well as "his vision and leadership in articulating the advantages and benefits to be realized from the Space Telescope Program."The US$720 million Spitzer was launched on 25 August 2003 at 05:35:39 UTC from Cape Canaveral SLC-17B aboard a Delta II 7920H rocket. It follows a heliocentric instead of geocentric orbit and drifting away from Earth's orbit at 0.1 astronomical units per year. The primary mirror is 85 centimeters in diameter, f/12, made of beryllium and was cooled to 5.5 K. The satellite contains three instruments that allow it to perform astronomical imaging and photometry from 3.6 to 160 micrometers, spectroscopy from 5.2 to 38 micrometers, spectrophotometry from 5 to 100 micrometers.
By the early 1970s, astronomers began to consider the possibility of placing an infrared telescope above the obscuring effects of Earth's atmosphere. In 1979, a report from the National Research Council of the National Academy of Sciences, A Strategy for Space Astronomy and Astrophysics for the 1980s, identified a Space Infrared Telescope Facility as "one of two major astrophysics facilities for Spacelab", a Shuttle-borne platform. Anticipating the major results from an upcoming Explorer satellite and from the Shuttle mission, the report favored the "study and development of... long-duration spaceflights of infrared telescopes cooled to cryogenic temperatures." The launch in January 1983 of the Infrared Astronomical Satellite, jointly developed by the United States, the Netherlands, the United Kingdom, to conduct the first infrared survey of the sky, whetted the appetites of scientists worldwide for follow-up space missions capitalizing on the rapid improvements in infrared detector technology.
Earlier infrared observations had been made by both ground-based observatories. Ground-based observatories have the drawback that at infrared wavelengths or frequencies, both the Earth's atmosphere and the telescope itself will radiate strongly. Additionally, the atmosphere is opaque at most infrared wavelengths; this necessitates lengthy exposure times and decreases the ability to detect faint objects. It could be compared to trying to observe the stars at noon. Previous space observatories were launched during the 1980s and 1990s and great advances in astronomical technology have been made since then. Most of the early concepts envisioned repeated flights aboard the NASA Space Shuttle; this approach was developed in an era when the Shuttle program was expected to support weekly flights of up to 30 days duration. A May 1983 NASA proposal described SIRTF as a Shuttle-attached mission, with an evolving scientific instrument payload. Several flights were anticipated with a probable transition into a more extended mode of operation in association with a future space platform or space station.
SIRTF would be a 1-meter class, cryogenically cooled, multi-user facility consisting of a telescope and associated focal plane instruments. It would be launched on the Space Shuttle and remain attached to the Shuttle as a Spacelab payload during astronomical observations, after which it would be returned to Earth for refurbishment prior to re-flight; the first flight was expected to occur about 1990, with the succeeding flights anticipated beginning one year later. However, the Spacelab-2 flight aboard STS-51-F showed that the Shuttle environment was poorly suited to an onboard infrared telescope due to contamination from the "dirty" vacuum associated with the orbiters. By September 1983 NASA was considering the "possibility of a long duration SIRTF mission". Spitzer is the only one of the Great Observatories not launched by the Space Shuttle, as was intended. However, after the 1986 Challenger disaster, the Centaur LH2–LOX upper stage, which would have been required to place it in its final orbit, was banned from Shuttle use.
The mission underwent a series of redesigns during the 1990s due to budget considerations. This resulted in a much smaller but still capable mission that could use the smaller Delta II expendable launch vehicle. One of the most important
Ohio is a Midwestern state in the Great Lakes region of the United States. Of the fifty states, it is the 34th largest by area, the seventh most populous, the tenth most densely populated; the state's capital and largest city is Columbus. The state takes its name from the Ohio River, whose name in turn originated from the Seneca word ohiːyo', meaning "good river", "great river" or "large creek". Partitioned from the Northwest Territory, Ohio was the 17th state admitted to the Union on March 1, 1803, the first under the Northwest Ordinance. Ohio is known as the "Buckeye State" after its Ohio buckeye trees, Ohioans are known as "Buckeyes". Ohio rose from the wilderness of Ohio Country west of Appalachia in colonial times through the Northwest Indian Wars as part of the Northwest Territory in the early frontier, to become the first non-colonial free state admitted to the union, to an industrial powerhouse in the 20th century before transmogrifying to a more information and service based economy in the 21st.
The government of Ohio is composed of the executive branch, led by the Governor. Ohio occupies 16 seats in the United States House of Representatives. Ohio is known for its status as both a bellwether in national elections. Six Presidents of the United States have been elected. Ohio is an industrial state, ranking 8th out of 50 states in GDP, is the second largest producer of automobiles behind Michigan. Ohio's geographic location has proven to be an asset for economic expansion; because Ohio links the Northeast to the Midwest, much cargo and business traffic passes through its borders along its well-developed highways. Ohio has the nation's 10th largest highway network and is within a one-day drive of 50% of North America's population and 70% of North America's manufacturing capacity. To the north, Lake Erie gives Ohio 312 miles of coastline. Ohio's southern border is defined by the Ohio River, much of the northern border is defined by Lake Erie. Ohio's neighbors are Pennsylvania to the east, Michigan to the northwest, Lake Erie to the north, Indiana to the west, Kentucky on the south, West Virginia on the southeast.
Ohio's borders were defined by metes and bounds in the Enabling Act of 1802 as follows: Bounded on the east by the Pennsylvania line, on the south by the Ohio River, to the mouth of the Great Miami River, on the west by the line drawn due north from the mouth of the Great Miami aforesaid, on the north by an east and west line drawn through the southerly extreme of Lake Michigan, running east after intersecting the due north line aforesaid, from the mouth of the Great Miami until it shall intersect Lake Erie or the territorial line, thence with the same through Lake Erie to the Pennsylvania line aforesaid. Ohio is bounded by the Ohio River, but nearly all of the river itself belongs to Kentucky and West Virginia. In 1980, the U. S. Supreme Court held that, based on the wording of the cessation of territory by Virginia, the boundary between Ohio and Kentucky is the northern low-water mark of the river as it existed in 1792. Ohio has only that portion of the river between the river's 1792 low-water mark and the present high-water mark.
The border with Michigan has changed, as a result of the Toledo War, to angle northeast to the north shore of the mouth of the Maumee River. Much of Ohio features glaciated till plains, with an exceptionally flat area in the northwest being known as the Great Black Swamp; this glaciated region in the northwest and central state is bordered to the east and southeast first by a belt known as the glaciated Allegheny Plateau, by another belt known as the unglaciated Allegheny Plateau. Most of Ohio is of low relief, but the unglaciated Allegheny Plateau features rugged hills and forests; the rugged southeastern quadrant of Ohio, stretching in an outward bow-like arc along the Ohio River from the West Virginia Panhandle to the outskirts of Cincinnati, forms a distinct socio-economic unit. Geologically similar to parts of West Virginia and southwestern Pennsylvania, this area's coal mining legacy, dependence on small pockets of old manufacturing establishments, distinctive regional dialect set this section off from the rest of the state.
In 1965 the United States Congress passed the Appalachian Regional Development Act, an attempt to "address the persistent poverty and growing economic despair of the Appalachian Region." This act defines 29 Ohio counties as part of Appalachia. While 1/3 of Ohio's land mass is part of the federally defined Appalachian region, only 12.8% of Ohioans live there Significant rivers within the state include the Cuyahoga River, Great Miami River, Maumee River, Muskingum River, Scioto River. The rivers in the northern part of the state drain into the northern Atlantic Ocean via Lake Erie and the St. Lawrence River, the rivers in the southern part of the state drain into the Gulf of Mexico via the Ohio River and the Mississippi; the worst weather disaster in Ohio history occurred along the Great Miami River in 1913. Known as the Great Dayton Flood, the entire Miami River watershed flooded, including the downtown business district of Dayton; as a result, the Miami Conservancy District was created as the first major flood plain engineering project in Ohio and the United States.
Grand Lake St. Marys in the west-central part of the state was constructed as a supply of water for ca