Question: What is the experimental satellite that was the forerunner to communication satellite of the operator of INSAT-4CR called?

Context paragraphs:
paragraph_text: INSAT-4CR was launched on 2 September 2007 by the fifth flight of the Geosynchronous Satellite Launch Vehicle, GSLV-F04. The launch occurred at 12:51 UTC on 2 September 2007. The third stage of the carrier rocket underperformed, resulting in the satellite being placed into a lower than planned orbit.
title: INSAT-4CR
paragraph_text: NOAA-4, also known as ITOS-G was a weather satellite operated by the National Oceanic and Atmospheric Administration (NOAA). It was part of a series of satellites called ITOS, or improved TIROS. NOAA-4 was launched on a Delta rocket on November 15, 1974. The launch carried two other satellites: AMSAT-OSCAR 7 and Intasat. It remained operational for 1463 days until it was deactivated by NOAA on November 18, 1978.
title: NOAA-4
paragraph_text: Optus can trace its beginnings back to the formation of the Government-owned AUSSAT Pty Limited in 1981. In 1982, Aussat selected the Hughes 376 for their initial satellites, with the first, AUSSAT A1, launched in August 1985. AUSSAT satellites were used for both military and civilian satellite communications, and delivering television services to remote outback communities.
title: Optus
paragraph_text: ATS - 6 (Applications Technology Satellite - 6) was a NASA experimental satellite, built by Fairchild Space and Electronics Division It has been called the world's first educational satellite as well as world's first experimental Direct Broadcast Satellite as part of the Satellite Instructional Television Experiment between NASA and Indian Space Research Organisation (ISRO). It was launched May 30, 1974, and decommissioned July 1979. At the time of launch, it was the most powerful telecommunication satellite in orbit. ATS - 6 carried no fewer than 23 different experiments, and introduced several breakthroughs. It was the first 3 - axis stabilized spacecraft in geostationary orbit. It was also the first to use experimentally with some success electric propulsion in geostationary orbit. It also carried several particle physics experiments, including the first heavy ion detector in geostationary orbit.
title: ATS-6
paragraph_text: The BeiDou Navigation Satellite System (BDS, simplified Chinese: 北斗卫星导航系统; traditional Chinese: 北斗衛星導航系統; pinyin: Běidǒu wèixīng dǎoháng xìtǒng) is a Chinese satellite navigation system. It consists of two separate satellite constellations – a limited test system that has been operating since 2000, and a full-scale global navigation system that is currently under construction.
title: BeiDou
paragraph_text: BeiDou-1 is an experimental regional navigation system, which consists of four satellites (three working satellites and one backup satellite). The satellites themselves were based on the Chinese DFH-3 geostationary communications satellite and had a launch weight of 1,000 kilograms (2,200 pounds) each.
title: BeiDou
paragraph_text: INSAT-4CR is a communications satellite operated by ISRO as part of the Indian National Satellite System. Launched in September 2007, it replaced the INSAT-4C satellite which had been lost in a launch failure the previous year. The satellite is stationed in geostationary orbit at a longitude of 74 degrees east, and is expected to operate for ten years, however this may have been reduced by the underperformance of the Geosynchronous Satellite Launch Vehicle which placed it into orbit. INSAT-4CR is planned to be replaced by GSAT-31, which was launched on February 6, 2019.
title: INSAT-4CR
paragraph_text: The A2100 is a communications satellite spacecraft model made by Lockheed Martin Space Systems in the 1990s-2010s for telecommunications in geosynchronous orbit, as well as GOES-R weather satellites and GPS Block IIIA satellites.
title: Lockheed Martin A2100
paragraph_text: NigComSat-1, a Nigerian satellite built in 2004, was Nigeria's third satellite and Africa's first communication satellite. It was launched on 13 May 2007, aboard a Chinese Long March 3B carrier rocket, from the Xichang Satellite Launch Centre in China. The spacecraft was operated by NigComSat and the Nigerian Space Agency, NASRDA. On 11 November 2008, NigComSat-1 failed in orbit after running out of power because of an anomaly in its solar array. It was based on the Chinese DFH-4 satellite bus, and carries a variety of transponders: 4 C-band; 14 Ku-band; 8 Ka-band; and 2 L-band. It was designed to provide coverage to many parts of Africa, and the Ka-band transponders would also cover Italy.
title: Nigeria
paragraph_text: Compass-M1 is an experimental satellite launched for signal testing and validation and for the frequency filing on 14 April 2007. The role of Compass-M1 for Compass is similar to the role of the GIOVE satellites for the Galileo system. The orbit of Compass-M1 is nearly circular, has an altitude of 21,150 km and an inclination of 55.5 degrees.
title: BeiDou
paragraph_text: The first and historically most important application for communication satellites was in intercontinental long distance telephony. The fixed Public Switched Telephone Network relays telephone calls from land line telephones to an earth station, where they are then transmitted to a geostationary satellite.  The downlink follows an analogous path.  Improvements in submarine communications cables through the use of fiber-optics caused some decline in the use of satellites for fixed telephony in the late 20th century.
title: Communications satellite
paragraph_text: Arianespace was contracted to launch INSAT - 4B using an Ariane 5 ECA carrier rocket. The launch occurred on 11 March 2007 at 22: 03 UTC, from ELA - 3 at Kourou. The Skynet 5A military communications satellite for the British Ministry of Defence was launched aboard the same rocket.
title: INSAT-4B
paragraph_text: The "Hipparcos" satellite was launched (with the direct broadcast satellite TV-SAT2 as co-passenger) on an Ariane 4 launch vehicle, flight V33, from Kourou, French Guiana, on 8 August 1989. Launched into a geostationary transfer orbit, the Mage-2 apogee boost motor failed to fire, and the intended geostationary orbit was never achieved. However, with the addition of further ground stations, in addition to ESA operations control centre at ESOC in Germany, the satellite was successfully operated in its geostationary transfer orbit for almost 3.5 years. All of the original mission goals were, eventually, exceeded.
title: Hipparcos
paragraph_text: TDRS-6, known before launch as TDRS-F, is an American communications satellite which is operated by NASA as part of the Tracking and Data Relay Satellite System. It was constructed by TRW, and is based on a custom satellite bus which was used for all seven first generation TDRS satellites.
title: TDRS-6
paragraph_text: Because of this shift in meaning, the term moon, which had continued to be used in a generic sense in works of popular science and in fiction, has regained respectability and is now used interchangeably with natural satellite, even in scientific articles. When it is necessary to avoid both the ambiguity of confusion with Earth's natural satellite the Moon and the natural satellites of the other planets on the one hand, and artificial satellites on the other, the term natural satellite (using ``natural ''in a sense opposed to`` artificial'') is used. To further avoid ambiguity, the convention is to capitalize the word Moon when referring to Earth's natural satellite, but not when referring to other natural satellites.
title: Natural satellite
paragraph_text: SICRAL 1B is a military communications satellite built by Thales Alenia Space for Italian Armed Forces. It is a dual-use spacecraft: Telespazio will use some of the satellite's transmission capacity and some will be used by the Italian defense ministry and NATO. The spacecraft is based on the Italsat 3000 bus and includes one EHF/Ka band, three UHF-band and five active SHF-band transponders. It is designed to be operable for 13 years.
title: SICRAL 1B
paragraph_text: As of 2009, Internet via satellite had a steady growth rate of 10% to 15% per year. It was particularly in demand in remote areas that did not have either dialup or wireless online services. The local telecommunications company Dalkom Somalia provided internet over satellite, as well as premium routes for media operators and content providers, and international voice gateway services for global carriers. It also offered inexpensive bandwidth through its internet backbone, whereas bandwidth ordinarily cost customers from $2,500 to $3,000 per month through the major international bandwidth providers. The main clients of these local satellite services were internet cafes, money transfer firms and other companies, as well as international community representatives. In total, there were over 300 local satellite terminals available aross the nation, which were linked to teleports in Europe and Asia. Demand for the satellite services gradually began to fall as broadband wireless access rose. However, it increased in rural areas, as the main client base for the satellite services extended their operations into more remote locales.
title: Communications in Somalia
paragraph_text: The Molniya orbit is designed so that the satellite spends the great majority of its time over the far northern latitudes, during which its ground footprint moves only slightly. Its period is one half day, so that the satellite is available for operation over the targeted region for six to nine hours every second revolution. In this way a constellation of three Molniya satellites (plus in-orbit spares) can provide uninterrupted coverage.
title: Communications satellite
paragraph_text: Hans K. Ziegler (March 1, 1911, Munich, Germany – December 11, 1999 Colts Neck Township, New Jersey, United States) was a pioneer in the field of communication satellites and the use of photovoltaic solar cells as a power source for satellites.
title: Hans K. Ziegler
paragraph_text: FedSat (Australia's 'Federation Satellite') is an Australian scientific research satellite launched from Tanegashima Space Center, Japan by a NASDA H-IIA launch vehicle in December 2002 (NASDA is now merged with JAXA). The satellite was developed by the Cooperative Research Centre for Satellite Systems, a cooperative made up of several universities, commercial organisations and government bodies. The ground station is at the Institute for Telecommunications Research, part of the University of South Australia, near Adelaide. Since 2005 it was operated by the Australian Department of Defence.
title: FedSat

Reasoning steps:
INSAT-4CR >> operator >>>> ISRO
the experimental satellite which was forerunner to communication satellite of ISRO is called >>>> ATS - 6 (Applications Technology Satellite - 6)

Answer: spans: ATS - 6 (Applications Technology Satellite - 6)