Thomas Passvogel

A Φ 3.5m diameter Sic telescope for Herschel mission

Since ten years ASTRIUM has developed sintered Silicon Carbide (SiC) technology for space applications. Its unique thermo-mechanical properties, associated with its polishing capability, make SiC an ideal material for building ultra-stable lightweight space based telescopes or mirrors. SiC is a cost effective alternative to Beryllium and the ultra-lighweighted ULE. In Complememt to the material manufacturing process, ASTRIUM has developed several assembly techniques (bolting, brazing, bonding) for manufacturing large and complex SiC assemblies. This technology is now perfectly mature and mastered. SiC is baselined for most of the telescopes that are developed by ASTRIUM. SiC has been identified as the most suitable material for manufacturing very large crygenic telescopes. In this paper we present the development of Φ 3.5 m telescope for Herschel Mission. Herschel main goal is to study how the first stars and galaxies were formed and evolved. The Herschel Space telescope, using silicon carbide technology will be the largest space imagery telescope ever launched. The Herschel telescope will weight 300 kg rather than the 1.5 tons required with standard technology. The Herschel telescope is to be delivered in 2005 for a launch planned for 2007.

Current status of the Herschel/Planck program

The Herschel/Planck ESA programme combines two ESA missions of the HORIZON 2000 programme, the cornerstone mission Herschel (formerly named Far InfraRed and Submillimetre Telescope - FIRST) and the third medium sized mission, Planck. Herschel is a multi-user observatory, observing in the far infrared and sub-millimetre part of the electromagnetic spectrum, in the wavelength range from 60 to 670 mm. The Planck mission is a survey mission dedicated to map the anisotropies of the temperature of the cosmic background radiation. Both missions are planned to be launched in February 2007 on a single Ariane V launcher from the European Space Port of Kourou in a dual launch configuration. Both missions use orbits around the 2nd Lagrangian libration point L2, that is approximately 1.5 million kilometres away from the earth in the anti-sun direction. The programme started the spacecraft development phase in April 2001 and will complete the design phase in Summer 2002. The paper gives an overview of the Herschel and Planck System Design and the project status

Very wide band telescope for Planck using optical and radio frequency techniques

Planck associated to FIRST is one of the ESA scientific missions belonging to the Horizon 2000 program. It will be launched by an Ariane 5 in 2007. Planck aims at obtaining very accurate images of the Cosmic Microwave Background fluctuations, thanks to a spaceborne telescope featuring a wide wavelength range and an excellent control of straylight and thermal variations.

FIRST/Planck mission cryogenic systems: current status

ESA is studying the possibility to merge two of the next scientific missions of its HORIZON 2000 Programme, the fourth cornerstone mission, the far IR and sub-millimeter telescope (FIRST) and the third medium-sized mission M3, Planck. FIRST is a multi-user observatory, which targets the IR and sub-millimeter part of the electromagnetic spectrum, in the wavelength range from 85 micrometers to 600 micrometers . The Planck mission is a survey mission dedicated to mapping the temperature anisotropies of the cosmic background radiation. The merger of the mission is presently being studied in view of the programmatic constraints on both missions, the fact that they use a similar orbit, the partial parallel development of both missions and the potential cost savings. The cryogenic system of FIRST is based on a Superfluid Helium Dewar at 1.65K with a design lifetime of more than 4.5 years. The very low temperature, required in the bolometer instrument will be obtained from a dedicated 3He-sorption cooler. The cryogenic system of Planck uses a sequence of passive radiator, H2 Joule-Thomson Sorption cooler, JT mechanical cooler, and dilution refrigerator.

FIRST/Planck program: current status

The FIRST/Planck ESA program combines two ESA missions of the HORIZON 2000 program, the cornerstone mission of the Far InfraRed and Submillimeter Telescope and the third medium sized mission, Planck. An overview is given in this paper of the current system design, the performance parameters and an outlook on the spacecraft development.

A very wide band telescope for Planck using optical and radio frequency techniques

Planck associated to FIRST is one of the ESA scientific missions belonging to the Horizon 2000 programme. It will be launched by an Ariane 5 in 2007. Planck aims at obtaining very accurate images of the Cosmic Microwave Background fluctuations, thanks to a spaceborne telescope featuring a wide wavelength range and an excellent control of straylight and thermal variations. The telescope is based on an off-axis gregorian design consisting of two concave ellipsoidal mirrors with a 1.5-meter pupil, derived from radio frequency antenna, but with a very wide spectral domain which ranges from far infrared (350 μm) up to millimetric wavelengths (10 mm). Its field of view is large (10 degrees) owing to a high number of detectors in the focal plane. The short wavelength detectors (bolometers operating at 0.1 K) are located at the centre of the focal plane unit while the long wavelength ones (based on HEMT amplifier technology operating at 20 K) are located at the periphery. The Planck telescope operates at a temperature below 60 K. This level is achieved in a passive way, i.e. using a cryogenic radiator. Furthermore, this radiator must accommodate a set of coolers dedicated to the focal plane unit, cooling one of the experiments down to 0.1 K. The Planck mission leads to very stringent requirements (straylight, thermal stability) that can only be achieved by designing the spacecraft at system level, combining optical, radio frequency and thermal techniques in order to achieve the required performance.

PLANCK AN OVERVIEW OF THE SPACECRAFT

The two science missions Herschel, an observatory‐type mission, and Planck, a survey mission, are combined in one program within ESA’s long‐term science program. This paper deals with Planck. The objective for Planck is to image systematically the whole sky simultaneously with two scientific instruments in nine frequency channels between 30 and 900 GHz to unravel the temperature fluctuations, i.e. the anisotropy, of the cosmic background radiation. Both satellites, have been launched together from the European Space Port in Kourou, French Guiana, on a single Ariane 5 launcher, the orbits will be Lissajous orbits around the 2nd Lagrange Point, “so called” L2 of the Earth‐Sun system. This paper gives an overview of the Planck spacecraft including the scientific instruments and the on ground testing.

Management of the Herschel/Planck Programme

The development of the Herschel and Planck Programme, the largest scientific space programme of the European Space Agency (ESA), has culminated in May 2009 with the successful launch of the Herschel and Planck satellites onboard an Ariane 5 from the European Spaceport in Kourou. Both satellites are operating flawlessly since then and the scientific payload instruments provide world-class science. The Herschel/Planck Programme is a multi national cooperation with the managerial lead being taken by the European Space Agency with the major contributions from European industry for the spacecraft development and from scientific institutes, organized in five international consortia, for the payload instruments. The overall programme complexity called for various, adapted, management approaches to resolve technical and programmatic difficulties. Some of the management experiences of over a decade needed to realize such a satellite programme will be presented giving the lessons learnt for future programmes with the similar complexities.