Contents

1. Experiments to be flown

2. Short description of the spacecraft

3. Use of knowledge, information and equipment resulting from the work already done under the preliminary contract for the TD1/TD2 satellites

4. Time scale to completion

5. Methods and means of control by the Organisation

6. Revision clause for this Annex

1. EXPERIMENTS TO BE FLOWN

The TD-1 satellite is intended to enable the operation in space of a group of seven scientific experiments.

Two of these experiments shall study the high energy X-ray spectrum of the sun and require one axis of the satellite to be permanently pointed at the sun. Four experiments shall scan the sky in several regions of the electromagnetic spectrum (UV and infrared), to study the emission from stars and other galactic or possible extragalactic sources, with different degrees of spectral and directional precision. These experiments shall take advantage of a slow continuous rotation of the satellite around the axis pointing at the sun. One experiment shall measure the composition of primary cosmic particles of cosmic and solar origin as well as the fluxes of protons coming from the sun and those trapped in the Van Allen belts.

The list of the actual experiments to be flown is given below.

Solar gamma and X-ray experiments:

S.88 : Solar gamma-ray detection in the energy range 50-300 MeV

- Scintillator/photomultiplier arrangement

- Experiment sponsored by the Physical Institute of the University of Milan.

S.100 : Monitoring of solar X-rays in the energy range 20-300 KeV

- Scintillator/photomultiplier arrangement.

- Experiment sponsored by the Space Research Laboratory of the Utrecht University.

Stellar UV radiation experiment:

S.1/2/68 : Multicolour celestial scanning in the spectral region 1000-3000 A and in the infrared

- 30 cm diameter telescope and associated spectrometer/ photometers/infrared detectors arrangement.

- Experiment jointly sponsored by the University of Liege and the Edinburgh Royal Observatory.

S.59 : UV stellar spectrometer

- 26 cm diameter telescope and spectrophotometer arrangement.

- Experiment sponsored by the Space Research Laboratory of the Utrecht University.

Stellar gamma and X-ray experiments:

S.133 : Measurement of gamma-rays in the energy range 70-300 MeV

- Optical spark chamber/counters/ Vidicon system arrangement.

- Experiment jointly sponsored by the Physical Institute of the University of Milan, the Munich Institute for Extra-Terrestrial Physics and the Saclay Nuclear Research Institute.

S.77 : Spectrometry of extra-terrestrial X-rays in the energy range 3-30 KeV

- X-ray collimator and proportional counters arrangement

- Experiment sponsored by the Saclay Nuclear Research Institute.

Cosmic ray charge distribution experiment:

S.67 A : Spectrometry of primary charged particles.

- Solid state detectors and Cerenkov counter.

- Experiment sponsored by the Saclay Nuclear Research Institute.

The TD-1 satellite shall be designed in order to accommodate the seven above-mentioned experiments. If, in the development of the project, serious difficulties make it necessary to consider a change in the composition of the payload, this would be treated in accordance with the existing ESRO procedure for the modification of satellite payloads resulting from development difficulties.

2. SHORT DESCRIPTION OF THE SPACECRAFT

The satellite shall consist essentially of two boxes, one containing the experiments and the other, mounted beneath it, containing the functional spacecraft equipment. The experiment compartment shall be built around the two large telescopes S.I/2/68 and S.59 and the spark chamber S.I33. The equipment compartment shall house the equipment necessary for the functioning of the satellites, e.g. the attitude control subsystem, the command receiver and decoders, the housekeeping subsystem, the data storage and transmission subsystem, the power conditioning, storage and distribution units. The satellite shall be powered by solar cells, mounted on solar paddles, hinged from opposite edges of the same face of the satellite body. This face of the satellite shall be controlled to face the sun during the sun-lit phase of the orbit with an accuracy of the order of 1 minute of arc.

Telecommand and telemetry transmissions shall take place in the V.H.F. band, through an antenna located at the tip of a deployable boom.

The satellite dimensions shall be about 1 x 0,9 x 2 m. Its weight shall be approximately 460 kg.

The satellite shall be launched into a quasi circular orbit at about 550 km altitude by a Thor Delta vehicle. The inclination of the orbit and time of launch shall be selected so that a sun-synchronous orbit is achieved. The satellite shall be designed to operate during the sun-lit phase of such an orbit only and for a maximum life time of 6 months.

Three satellite units shall be produced:

- a first prototype model P 1

- a qualification model P 2

- the flight model.

3. USE OF KNOWLEDGE, INFORMATION, AND EQUIPMENT RESULTING FROM THE WORK ALREADY DONE UNDER THE PRELIMINARY CONTRACT FOR THE TD 1/TD 2 SATELLITES

All information and knowledge already accumulated under the preliminary contract for the TD 1/TD 2 satellites, at the contractor and in the Organisation, shall be made available to the TD project, wherever this is of use for the implementation of that project. Equipment already developed or under construction in the framework of the preliminary contract for the TD1/TD2 satellites shall be used, wherever possible, for the benefit of the TD project.

The TD project shall be conducted in such a way that the fullest use shall be made of the knowledge accumulated and of the equipment developed under the preliminary contract for the TD1/TD2 satellites.

4. TIME-SCALE TO COMPLETION

The TD project shall be conducted so as to lead to the earliest possible launch date compatible with a high probability of success in orbit. The overall time-scale for the project shall take into account the necessity of ensuring a reasonable separation between the end of the tests on the first satellite prototype PI and the delivery of experiments and equipment for integration into the qualification satellite model P2.

Recognizing that the mission requirements can only be met if launch takes place during short windows in Spring and Autumn each year, a launch in Spring 1972 shall be set as a target for the TD satellite.

The Organization shall endeavour to assist the scientific groups involved in meeting the most economical time-scale leading to a launch in Spring 1972.

5. METHODS AND MEANS OF CONTROL BY THE ORGANISATION

The Organisation shall aim at ensuring the best possible control of the TD project, as regards technical performances, time-scale and costs.

To achieve this goal, the Organisation shall set up a project group, containing an adequate number of suitably qualified specialists. This project group shall constitute an integral part of ESTEC. Its function shall be to monitor the works for which the prime contractor is responsible, to monitor the works which are undertaken within the Organisation and directly concerned with the execution of the project and to ensure the compatibility of interfaces throughout the project. The project group shall comprise only persons working exclusively for the TD project. The size of this group shall be approximately 50 persons.

The TD project group shall receive as need be, the assistance of functional support divisions of the Organisation.

Adequate modern control techniques shall be used in the conduct of the project. These methods shall enable the project managers in industry and in ESRO to know at regular intervals the overall situation of the project as regards technical progress, time-scale and cost and to compare it with reference plans forming part of the development contract. The corresponding control procedures shall be made parts of the contractual obligations imposed on the prime contractor and his co- and sub-contractors.