HIFI (Heterodyne Instrument for the Far Infrared) spectrometer was one of the three scientific instruments, which has been placed on the space observatory HERSCHEL. It was built by a consortium led under the responsibility of the Principal Investigator Prof. Thijs de Graauw from Space Research Organization of Netherlands.

Since very complicated HIFI construction and for using the latest achievements in submilimeter technology, superconducting and low temperature physics, it was decided to build the following seperated modules:

• optical input block containing detectors, mixers and pre-amplifiers,
• local oscillator working in temperature about 100K (-173C),
• output block containing intermediate frequency amplifiers and spectrometers,
• HIFI control unit for instrument control, communication with satellite and transmission scientific data.

The main task of SRC PAS was construction of HIFI Local Oscillator Control Unit (HLCU) for Local Oscillator Subsystem. SRC group was responsible of delivering about 100 Watts secondary power spread among of more than 120 different, floating and programmable (in most of the cases) rails. The rails supply the 30 GHz synthesizer, microwave amplifiers and bias the microwave multipliers in 14 frequency bands (chains).

80C32 microcontroller, 32KBytes of RAM, 16 Kbytes of PROM and RTX54SX32S FPGA from Actel are used in digital block. The software implemented in our unit, written in Assembler, controls the safety operations of the whole Local Oscillator Subsystem and, by this, fulfills one of the most critical and difficult tasks in HIFI. In addition more than 180 analogue channels are monitored by our system with 12 bits resolution, some of them are used internally in Local Oscillator for self checking, the others are distributed to Herschel telemetry system.

The 15 kg Local Oscillator Control Unit (LCU) presents fully redundant system designed according to ESA requirements. This is the biggest and the most complicated electronics block manufactured up to now in SRC according to strict ESA rules.

HERSCHEL was launched on 14 May 2009 at 15:12 (CEST) by Ariane rocket.

Following extensive investigations of the anomaly in early August 2009, all HIFI subsystems were successfully switched on again in January 2010 (including Redundant LCU unit). The new software was uploaded to LCU memory and the instrument has been back with its full capability. The software contains the new procedures for calculating checksums of different parts of LCU memory (so called “safe”, “critical” and “tables”). The procedures are used for cyclic LCU memory with the regards of SEU efect. 27 SEUs were observed in LCU in 2010. Recovery from such events has become very much routine and operationally the situation is fully under control.

HERSCHEL studies the origin of stars and galaxies but it also keeps on searching for water in space. It helps us to understand the formation of our own Solar System through detailed observations of comets and of the poorly known 'transneptunian objects'. HERSCHEL is the first space observatory covering a major part of the far-infrared and submillimetre waveband (from 100 to 625 microns). The HIFI instrument continues to experience an occasional SEU in the Local Control Oscillator Unit. In the majority of these cases, science data are not affected, either because the instrument is not prime, or because non-critical memory is affected.

All time the HIFI instrument has been continuously producing excellent quality science data. HIFI has already resulted in more than 60 scientific articles. A lot of interesting observation data has been collected during the whole year of HIFI instrument operations. One of the first data obtained with HIFI is the spectrum which has revealed the chemical fingerprints of potential life-enabling organic molecules in the Orion Nebula, a nearby stellar nursery in our Milky Way galaxy. Then early results, reported in May at the Herschel First Results Symposium in ESTEC, demonstrate the detection of water in various proto-stellar systems. Along with upcoming data from star-forming clouds throughout the Milky Way, these data will help astronomers understand the mechanisms of star formation in great detail.

A second, unexpected result was the discovery of two new forms of water: charged water (OH+ and H2O+) and heavy water (D2O). The existence of charged water points to UV radiation: it does not occur naturally on earth but it can be produced in a laboratory with a strong radiation source. The high sensitivity and spectral resolution as well as the frequency coverage of HIFI spectrometer allows also to detect the emission lines of water in Solar System objects such as cometary comae and planetary atmospheres

The HIFI Local Oscillator Control Unit was presented at the International Exhibition of Innovation IWIS 2010, which was held in Warsaw on 20-22 October 2010. Piotr Orleański and his team were awarded the gold medal IWIS 2010 for developing this block on Herschel mission.

Currently Herschel is conducting routine science phase operations. On 28 February 2011 HIFI was hit by an SEU and brought to a full stop. SEUs are occasional occurrences, but this time the hit was in a critical area of the LCU memory - in the place where the checksum calculation is done. Furthermore, the LCU no longer responded to commanding. The only possible solution was power cycling (turning off and then on again) of the instrument from the Control Centre on Earth. After careful consideration and choosing the right conditions to do so, like the temperature of the electronics, it was decided to power cycle the LCU. This was carried out on 3 March 2011, which has successfully restored HIFI to normal operation. Since that time HIFI with LCU - Local Oscillator Control Unit, instrument built in SRC, for Local Oscillator Subsystem has operated correctly in the whole 2011.

On 8 February 2012 it was exactly 1000 days since Herschel's lift-off in Kourou. Space Observatory commenced its second thousand of Operational Days (OD). The present best estimate of the remaining cryogen lifetime predicts that Herschel will be performing science observations until approximately February 2013.

The Herschel was performing continuously the routine science phase operations with HIFI/LCU instrument during the whole 2012. However the Herschel operational large halo orbit around L2 is unstable, and thus needs regular maintenance. Consequently, after end-of-helium (expected in March 2013), the spacecraft will need to be "parked" somewhere else with no need of orbit maintenance (sometimes referred to as "disposal" or "de-orbiting"). The baseline has been to put the spacecraft in heliocentric orbit.

Science observing performed with the instruments of Herschel spacecraft was continued until end-of-helium which took place on 29 April 2013. But the stalwart satellite continued providing value to the end, serving as an orbiting testbed for control techniques that can’t normally be tested in flight. At last mission controllers in ESOC sent the final command to the Herschel satellite on 17 June 2013 at 12:25 GMT (14:25 CEST), marking the end of operations for ESA’s hugely successful space observatory. Earlier it was ensured that all fuel is depleted and the satellite was boosted away from its operational orbit around the L2 Sun–Earth Lagrange Point into a safe heliocentric orbit.

more about LCU.