Interestingly I can't find any TLEs for Vela 1A (1963-039C, 00692) between April 1968 and October 2014! It was inserted into the nearly circular orbit described in your Wikipedia article, but when it re-appeared in the catalog it had an eccentricity in the 0.54 to 0.57 ballpark, and by 2018 this had risen to 0.64.
The Heavens-Above site is using the last available TLE from August 2018, and this will be the best set of values to use. Although bear in mind that the orbit is changing over time and even this TLE is already out-of-date. So the information therein will not be entirely accurate.
Prior to this, Heavens-Above used TLEs dated July 2017, March 2016 and March 1968. Data from all of these TLEs is given below and we can see from these how the eccentricity of Vela 1A's orbit increased over time.
As an aside, there seems to be two naming conventions. Two spacecraft were launched each time. One convention calls them A and B, the other n
and n+1
. So Vela 6A and 6B are also called Vela 11 and 12.
**TLE dated 24th August 2018:**
The orbit data is extracted from the following two-line orbital elements,
1 692U 63039C 18236.14976426 -.00001479 +00000-0 +00000-0 0 9999
2 692 027.2026 342.0351 6396976 210.0920 087.3147 00.22178276044278
Epoch (UTC): 24 August 2018 03:35:39
Eccentricity: 0.6396976
inclination: 27.2026°
perigee height: 35160 km
apogee height: 182657 km
right ascension of ascending node: 342.0351°
argument of perigee: 210.0920°
revolutions per day: 0.22178276
mean anomaly at epoch: 87.3147°
orbit number at epoch: 4427

**TLE dated 3rd March 2016:**
The orbit data is extracted from the following two-line orbital elements,
1 00692U 63039C 16063.84064408 -.00001506 00000-0 00000+0 0 9990
2 00692 37.4196 358.2839 5630613 170.2010 359.2879 0.22145093 42276
Epoch (UTC): 03 March 2016 20:10:31
Eccentricity: 0.5630613
inclination: 37.4196°
perigee height: 44045 km
apogee height: 174002 km
right ascension of ascending node: 358.2839°
argument of perigee: 170.2010°
revolutions per day: 0.22145093
mean anomaly at epoch: 359.2879°
orbit number at epoch: 4227
**TLE dated 24th March 1968:**
The orbit data is extracted from the following two-line orbital elements,
1 00692U 63039C 68084.10555552 -.00000374 +00000-0 +00000-0 0 00000
2 00692 036.7283 179.1791 0852721 237.5470 072.7561 00.22091344003596
Epoch (UTC): 24 March 1968 02:32:00
Eccentricity: 0.0852721
inclination: 36.7283°
perigee height: 99355 km
apogee height: 119068 km
right ascension of ascending node: 179.1791°
argument of perigee: 237.5470°
revolutions per day: 0.22091344
mean anomaly at epoch: 72.7561°
orbit number at epoch: 359