Editing Project Echo (section)

== Flights ==
Five suborbital ballistic tests to determine whether the launch, deploy, and expansion mechanisms would work were flown using the [[Shotput (rocket)|Shotput]] test vehicle, a three-stage rocket.<ref>{{Cite web |title=Shotput |url=https://space.skyrocket.de/doc_lau_det/shotput.htm |access-date=2024-03-21 |website=Gunter's Space Page }}</ref> The first Shotput flew at 5:40 pm on 27 October 1959.  Shotput 1 successfully delivered the Echo prototype to the desired altitude, but a small amount of residual gas in the folds of the balloon violently expanded, bursting the test article. People up and down the Atlantic coast witnessed what looked like distant fireworks as thousands of pieces of shredded Mylar reflected sunlight in a display that lasted for about 10 minutes.<ref name="hansen1995"/> Four more Shotput tests were flown on 16 January, 27 February, 1 April, and 31 May 1960.<ref>{{cite web|title=Shotput|url=http://www.astronautix.com/s/shotput.html|archive-url=https://web.archive.org/web/20161228060922/http://astronautix.com/s/shotput.html|url-status=dead|archive-date=28 December 2016|publisher=Astronautix|access-date=27 February 2021}}</ref>

On 13 May 1960, the first attempt to orbit an Echo satellite was made. The mission, which was also the maiden voyage of the [[Thor-Delta]] [[launch vehicle]], failed before deployment of the payload. Echo 1 lifted off from [[Cape Canaveral Space Force Station|Cape Canaveral]]'s [[Cape Canaveral Space Launch Complex 17|LC-17A]], and the [[Thor (rocket family)|Thor]] stage performed properly, but during the coasting phase, the attitude control jets on the unproven [[Delta (rocket family)|Delta]] stage failed to ignite, sending the payload into the [[Atlantic Ocean]] instead of into orbit.

On 12 August 1960, Echo 1A (commonly referred to as ''Echo 1'') was successfully put into an orbit of {{cvt|944|to|1048|mi|km}} by another Thor-Delta.<ref name="astr01"/><ref name="NSSDC ID:1960-009A">{{cite web|title=Echo 1|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1960-009A|publisher=NASA|access-date=8 October 2015}} {{PD-notice}}</ref> A microwave transmission from the JPL Goldstone facility in California, was relayed by the satellite to [[Bell Laboratories]] in Holmdel, New Jersey, that same day.<ref name=Jones1961/> It was originally expected that Echo 1A would not survive long after its fourth dip into the atmosphere in July 1963, although estimates allowed the possibility that it would continue to orbit until 1964 or beyond.<ref name=Jones1961>{{cite journal|title=Solar Radiation Pressure Effects, Gas Leakage Rates, and Air Densities Inferred From the Orbit Of Echo I|journal=Space Research II, Proceedings of the Second International Space Science Symposium, Florence, April 10–14, 1961|editor=H. C. Van De Hulst, C. De Jager and A. F. Moore|publisher=North-Holland Publishing Company-Amsterdam|year=1961|author1=Harrison M. Jones|author2=I. I. Shapiro|author3=P. E. Zadunaisky|quote=The observed variations of the Echo orbit - due primarily to the effects of the pressure of sunlight - are in excellent agreement with our theoretical results. The perigee altitude has an oscillation of large amplitude (approximately equal to {{cvt|600|km}}) and long period (approximately equal to 300 days), which has a decisive influence on the lifetime of Echo I. Our present best estimate is that the balloon will perish in the summer of 1963.}}</ref> It ended up surviving much longer than expected, and finally reentered Earth's atmosphere and burned up on 24 May 1968.

On 25 January 1964, Echo 2 was launched on a [[Thor Agena]] launch vehicle. In addition to passive communications experiments, it was used to investigate the dynamics of large spacecraft and for global geometric [[satellite geodesy|geodesy]]. Since it was larger than Echo 1A and orbiting in a near-polar orbit, Echo 2 was conspicuously visible to the unaided eye over all of the Earth. It reentered Earth's atmosphere and burned up on 7 June 1969.

Both Echo 1A and Echo 2 experienced a [[solar sail]] effect due to their large size and low mass.<ref>{{cite web|url=https://science.nasa.gov/headlines/y2008/31jul_solarsails.htm|title=A Brief History of Solar Sails|last=Coulter|first=Dauna|publisher=NASA|date=31 July 2008|access-date=4 February 2010|url-status=dead|archive-url=https://web.archive.org/web/20100128182259/http://science.nasa.gov/headlines/y2008/31jul_solarsails.htm|archive-date=28 January 2010}} {{PD-notice}}</ref> Later passive communications satellites, such as OV1-08 [[PasComSat]], solved the problems associated with this by using a grid-sphere design instead of a covered surface. Later yet, NASA abandoned passive communications systems altogether, in favor of active satellites.