Echo 1

  1960-009A

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A-11 was launched on 1960 Aug 12. This time the Delta and the Altair third stage worked well, and inserted a magnesium canister into a 1524 x 1684 km x 47.2 deg orbit. Two minutes after orbit insertion, the canister was blown open and the A-11 balloon was inflated; it was renamed Echo I. A-11 had two 107 MHz radio beacons to aid initial tracking, but was otherwise entirely passive once inflated. The communications tests were successful; the balloon remained pressurized until Jan 1961. It remained in orbit until 1968 May 24; in the meanwhile solar radiation pressure caused wide variations in its orbital parameters, as the table below illustrates. While the period remained roughly constant, the eccentricity oscillated between low and high values.

Echo 1
Date	Time	Event	Orbit
1960 Aug 12	0939:42	Launch by Delta	CC LC17A
	0942:21	T+2:39 MECO
	0942	Thor sep
	0942	Stage 2 burn 1:49
	0944:17	SECO T+4:35
		15 min coast
	0958?	Stage 2 (S/N 2012) sep	-4440? x 1517? x 47.3
	0959	Altair burn
	1000	Altair (S/N 3012) sep
		Canister open
	1001?	Inflation
1960 Aug 12			118.23 1517 x 1684 x 47.2
1960 Aug 24	0923	First shadow entry
1960 Sep 14			118.19 1448 x 1750 x 47.2
1960 Nov 22			117.63 1143 x 2005 x 47.3
1961 Jan 4			117.15 965 x 2140 x 47.3
1961 Jan 16		Loss of pressure
1961 Jan 22			117.16 1004 x 2102 x 47.3
1961 Mar 24			117.14 1129 x 1975 x 47.3
1961 May 30			117.11 1408 x 1693 x 47.3
1961 Sep 28			116.74 1193 x 1875 x 47.2
1961 Dec 10			116.23 905 x 2117 x 47.3
1962 Jan 31			116.28 1059 x 1967 x 47.3
1962 May 11			116.29 1503 x 1523 x 47.2
1962 Nov 14			115.50 947 x 2008 x 47.2
1963 Mar 31			115.52 1448 x 1509 x 47.2
1963 Sep 11			114.92 971 x 1931 x 47.2
1964 Feb 18			114.79 1408 x 1483 x 47.2
1964 Aug 7			114.14 918 x 1913 x 47.2
1965 Jan 3			114.12 1363 x 1467 x 47.2
1965 May 20			113.58 945 x 1836 x 47.2
1965 Jul 1			113.43 876 x 1891 x 47.2
1965 Nov 29			113.47 1322 x 1448 x 47.2
1966 May 22			112.66 879 x 1817 x 47.2
1966 Nov 5			112.33 1159 x 1507 x 47.3
1967 Mar 4			111.25 850 x 1718 x 47.3
1967 Aug 18			109.99 1152 x 1300 x 47.3
1968 Jan 6			107.13 719 x 1468 x 47.3
1968 Feb 24			104.36 761 x 1168 x 47.3
1968 May 10			99.30 665 x 785 x 47.2
1968 May 23			92.70 394 x 419 x 47.2
1968 May 24		Reentered