Vela 3A

{{short description|U.S. reconnaissance satellite}}

{{Infobox spaceflight

| name = Vela 3A

| image = Vela5b.jpg

| image_size = 180px

| image_caption = Vela satellite.

| mission_type =

| operator = USAF

| website =

| COSPAR_ID = 1965-058A{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1965-058A|title=Vela 3A|last=NASA GSFC|access-date=July 28, 2019}} {{PD-notice}}

| SATCAT = 1458

| mission_duration =

| spacecraft_bus =

| manufacturer = TRW

| dry_mass =

| launch_mass = {{convert|150|kg|lb}}

| power =

| launch_date = {{start-date|July 20, 1965, 08:27|timezone=yes}} UTC

| launch_rocket = Atlas Agena D 2A

| launch_site = Cape Canaveral LC-13

| launch_contractor =

| entered_service =

| disposal_type =

| deactivated =

| orbit_epoch = {{start-date|July 20, 1965}}

| orbit_reference = Geocentric

| orbit_regime = Highly Elliptical

| orbit_periapsis = {{convert|84,534|km|mi}}

| orbit_apoapsis = {{convert|96,238|km|mi}}

| orbit_inclination = 35.2°

| orbit_semimajor =

| orbit_eccentricity =

| orbit_period = 5,148.16 minutes

| apsis = gee

| programme = Vela

| previous_mission = Vela 2B

| next_mission = Vela 3B

}}

File:Atlas 225D with Vela 3A (Vela 5), Vela 3B (Vela 6) and ERS-17 satellites, July 20 1965.jpg

Vela 3A (also known Vela 5, Vela Hotel 5 and OPS 6577{{cite web|url=http://www.lib.cas.cz/www/space.40/1964/040A.HTM|title=1965-058A – Vela 3|work=Space 40|last=Antonín Vítek|access-date=July 28, 2019}}) was a U.S. reconnaissance satellite to detect explosions and nuclear tests on land and in space; the first of the third pair of Vela series satellites; taken together with Vela 3B and ERS 17 satellites.

The secondary task of the ship was space research (X-rays, gamma rays, neutrons, magnetic field and charged particles). Sister Vela 3B was in a similar orbit, but 180 degrees from it, i.e. on the opposite side of the globe.

The satellite was rotationally stabilized (2 rps). The ship could work in real time mode (one data frame per second) or in data recording mode (one frame every 256 seconds). The first mode was used for the first 40% of the mission's duration. About 1 transmission was received every 4 hours. The second mode was used until the next pair of Vela satellites were launched.

The ship remains in orbit around Earth.