ATS-4

{{Infobox spaceflight

| name = ATS-4, Advanced Tech. Sat. 4, ATS-D, PL-683A, 03344

| image = ATS-4.jpg

| image_size = 200px

| image_caption = ATS-4

| mission_type = Weather Satellite

| operator = NASA

| website =

| COSPAR_ID = 1968-068A

| SATCAT = 03344

| mission_duration = 38 days

| spacecraft_bus = HS-306

| manufacturer = Hughes Aircraft

| dry_mass =

| launch_mass = {{convert|305|kg|lb}}

| dimensions =

| power = 350 W (peak)

| launch_date = {{start-date|August 10, 1968, 22:33:00|timezone=yes}} UTC

| launch_rocket = Atlas SLV-3C Centaur-D (AC-17)

| launch_site = Cape Canaveral LC-36A

| launch_contractor =

| disposal_type = August 10, 1968

| deactivated =

| last_contact =

| decay_date = {{end-date|October 17, 1968}}

| orbit_epoch =

| orbit_reference = Geocentric

| orbit_regime = LEO

| orbit_periapsis = {{convert|185.99|km|mi}}

| orbit_apoapsis = {{convert|766.89|km|mi}}

| orbit_inclination = 29.141º

| orbit_eccentricity = 0.042372

| orbit_period = 94.131 minutes

| apsis = gee

| programme = Applications Technology Satellites

| previous_mission = ATS-3

| next_mission = ATS-5

}}

ATS-4 (Applications Technology Satellite) also known as ATS-D was a communications satellite launched by NASA on August 10, 1968{{cite web |last1=Garner |first1=Robert |title=ATS |url=https://www.nasa.gov/centers/goddard/missions/ats.html |website=Goddard Space Flight Center |publisher=NASA |access-date=22 April 2021 |archive-url=https://web.archive.org/web/20210226202828/http://www.nasa.gov/centers/goddard/missions/ats.html |archive-date=2021-02-26 |location=Greenbelt, MD |date=2010-01-22 |quote=ATS-4 was to investigate the possibilities of a gravity gradient stabilization system. A launch vehicle failure stranded ATS-4 in a much lower than planned orbit, making the satellite nearly useless. Despite this, NASA engineers successfully turned on several of the experiments to collect as much information as possible during the craft's short life. The low orbit and resulting atmospheric drag caused ATS-4 to re-enter Earth's atmosphere and break apart on Oct. 17, 1968. |url-status=live}} from Cape Canaveral through an Atlas-Centaur (AC-17) rocket.{{cite web |last1=Bell |first1=Ed |title=1968-068A |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1968-068A |website=NASA Space Science Data Coordinated Archive |publisher=NASA |access-date=22 April 2021 |archive-url=https://web.archive.org/web/20210121111558/https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1968-068A |archive-date=2021-01-21 |url-status=live}}

Objectives

The objective of ATS-4 was to investigate the possibilities of a gravity gradient stabilization system (the method of stabilizing artificial satellites).

Features

The satellite has a cylindrical shape with a {{convert|142|cm|adj=on}} diameter and {{convert|183|cm|adj=on}} height (about {{convert|360|cm}} considering the motor cover) with the surface covered by solar panels that generated a maximum of 350 W of power,{{cite web |author1=Fairchild Hiller Space Systems Division |author1-link=Fairchild Aircraft |title=ATS-4 study program, volume 4 Final report |url=https://ntrs.nasa.gov/api/citations/19670015278/downloads/19670015278.pdf |website=NTRS - NASA Technical Reports Server |publisher=NASA |access-date=22 April 2021 |archive-url=https://web.archive.org/web/20210422114758/https://ntrs.nasa.gov/api/citations/19670015278/downloads/19670015278.pdf |archive-date=22 April 2021 |location=Germantown, Maryland |page=64 |date=1 December 1966 |url-status=live}} and stabilized by gravity gradient. It was based on the Hughes Aircraft HS-306 bus.{{cite web |author1=Hughes Aircraft Company Space and Communications Group |author1-link=Hughes Aircraft Company |title=Tracking and data relay satellite system configuration and tradeoff study. Volume 5: TDRS spacecraft design, part 1 |url=https://ntrs.nasa.gov/api/citations/19740002695/downloads/19740002695.pdf |website=NTRS - NASA Technical Reports Server |publisher=NASA |access-date=22 April 2021 |archive-url=https://web.archive.org/web/20210422113252/https://ntrs.nasa.gov/api/citations/19740002695/downloads/19740002695.pdf |archive-date=22 April 2021 |location=El Segundo, California |page=269 |date=1972-09-29 |url-status=live}}

Instruments

A total of four experiments were conducted during the mission:

Mission

The Atlas and Centaur stages performed satisfactorily and placed the Centaur/ATS-4 in an elliptical parking orbit. However the Centaur stage failed to re-ignite after a 61-minute coast. The failure was determined to be freezing of the hydrogen peroxide supply lines to the Centaur engines.{{cite web |author1=Lewis Research Center |author1-link=Glenn Research Center |title=Atlas-Centaur AC-17 performance for applications technology satellite ATS-D mission |url=https://ntrs.nasa.gov/api/citations/19720017275/downloads/19720017275.pdf |website=NTRS - NASA Technical Reports Server |publisher=NASA |access-date=22 April 2021 |archive-url=https://web.archive.org/web/20210422110726/https://ntrs.nasa.gov/api/citations/19720017275/downloads/19720017275.pdf |archive-date=2021-04-22 |location=Cleveland, Ohio |date=1972-05-01 |url-status=live}}

High atmospheric drag due to the low altitude of the achieved orbit (186 km perigee) precipitated the orbital decay of the spacecraft. ATS-4 still achieved good results in some of the experiments, but the primary objective of achieving gravity gradient stabilization of a satellite was not reached.

ATS-4 reentered the atmosphere on 17 October 1968.

References

External links

[http://www.nasa.gov/centers/goddard/missions/ats.html ATS, Past NASA Missions]
[https://science.nasa.gov/missions/ats/ ATS, NASA Science Missions]

Category:1968 in spaceflight

Category:Applications Technology Satellites