Tuesday, 8 August 2017

The Ariel Satellite Programme - (Part 2)

As the end of 1971 drew near, the second half of the Ariel Satellite programme was to kick off. Having now launched satellites from three different locations, the Ariel team were to return to a familiar launch site in Vandenberg Air Force Base to launch Ariel 4.
It had been four and a half years since Ariel 3 and on the surface the satellites and missions appeared to be very similar. Like it’s predecessor, and all further Ariel missions, Ariel 4 was launched atop a Scout launch vehicle. This was on Dec 11th 1971.
Nearly 3 years later Ariel 5 was preparing for launch. Sat at the pointy end of it’s scout rocket, Ariel 5 was the only of it’s programme to be launched from the Broglio Space Centre; an Italian owned facility near Maklindi in Kenya. It was launched from the San Marco launch platform at sea on Oct 15th 1974.

A Scout Rocket on San Marco

Ariel 5 was a joint British and American venture and was an all sky monitor (or ASM) which was dedicated to observing the sky in the X-Ray band. Ariel 5 decayed from orbit on Mar 13th 1980.
The sixth and final Ariel satellite was launched on Jun 2nd 1979. Returning to Virgina; the Scout rocket launched from Wallops Island at launch area 3A. Loaded with high energy astrophysics experiments, Ariel 6 was operated until February 1982 where it then spent a solitary 8 years until finally decaying from Earth orbit on Sep 23rd 1990.

Ariel 4
Also known as UK-4 and 05675, Ariel 4 was designed to have a mission duration/operational lifespan of just one year. With mission specific experiments and a lower budget, all effort was made to make this as efficient and economic as possible.

Ariel 4 under construction

Similar in design to previous iterations of the Ariel satellites, Ariel 4 was equipped with four wide legs that extended outward and down from the base of the main cylinder. These were equipped with solar panels and experiments. The main cylindrical body was covered with solar cells and topped with a conical structure housing particle experiment equipment. The apex of the cone was thus oriented towards the northern geomagnetic pole. Although the tape recorded data was of low resolution, realtime reading of experimental data was high res.

The Satellite:
  • 99.5kg
  • Tape Recorder
  • 6 Experiments
    • Observations of radio noise
    • Electron density and temperature
    • Very low frequency (VLF) and extremely low frequency (ELF) propagation
    • VLF impulses
    • Characteristics of low-energy charged particles

Ariel 5
An All-Sky Monitor (ASM), Ariel 5 examined the sky in the X-Ray band. Fitted with two one-dimensional pinhole cameras, the satellite rotated 10 times a minute while orbiting the Earth between 400 and 500 km. Heavier than it’s predecessor, it weighed 139kg.

Ariel 5 Under Construction

Ariel 5

All of the data was stored as it was collected and then relayed to ground teams once every orbit. Each orbit was 1hr 36min. The main purpose of the experiments on Ariel 5 were to improve the accuracy of position measurement of X-ray stars and to measure their energy spectra.

The Satellite:
  • 38in Diameter
  • 34in Height
  • 6 Experiments
    • Rotation Modulation Collimator (RMC)
    • 2- to 10-KeV Sky Survey Instrument (SSI)
    • High-Resolution Source Spectra
    • Bragg Crystal Spectrometer (BCS)
    • High-Energy Cosmic X-Ray Spectra
    • All-Sky Monitor

Ariel 6
The final satellite of the programme. Ariel 6 was launched in 1979 and finally decayed in 1990. Designed to carry out a range of high energy astrophysics studies, it was manufactured by the Marconi company.

ariel 6.PNG
Ariel 6 under construction by Marconi Company

It carried six experiments, two X-Ray and one cosmic ray. Unfortunately radar signals interfered with the satellite and affected the data it returned from the remaining three tech experiments.

The Satellite:

  • 155kg
  • 6 Experiments
    • Cosmic Ray
    • X-Ray proportional counter spectrometer
    • X-Ray grazing incidence system
    • Three technology experiments (data not returned)

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