GENERAL PURPOSE Reference

Handheld Spectrum Analyzer R&S ® FSH3 Put to the test on board the International Space Station ISS

The R&S ® FSH3 (FIG 1) from Time signal system in the test means of a Progress space transporter phase and installed by the crew (FIG 3). Rohde & Schwarz is a high-end The global transmission services (GTS) spectrum analyzer in handheld design system is a new system for the world- Needed – a featherweight wide transmission of time signals high-tech analyzer that features low weight, minimum to receivers on the ground, such as watches or clocks in vehicles. It is cur- However, when the electronics unit was power consumption and outstanding rently being tested as part of a pilot initially put into operation in February experiment on board the ISS (FIG 2). 2002, it exhibited deviations from the RF performance [*]. It is currently This is the first commercial experiment precalculated receive field strength on aboard the space station. Once the test the ground. Nevertheless, the teleme- being used on board the International phase has been completed, the GTS try performed both on board the ISS and system is to be transferred to an opera- via the ground station exhibited nomi- Space Station (ISS) for distance-to- tor company. Owing to a recently devel- nal values. One of the possible reasons oped cryptographic modulation, further for this deviation may have been two RF fault (DTF) measurements. services such as vehicle theft protec- wiring harnesses that had already been tion or the tracking of specific items (e.g. installed prior to the launch and that containers or stolen goods) can also be had been in space for two years. The implemented. harnesses with a total length of 29 m are routed via special vacuum-tight The GTS system consists of an active coaxial ducts from the interior of the ser- phased array antenna outside the ISS vice module to the outside. Thus, they FIG 1 The R&S ® FSH3 with VSWR bridge for vector reflection measurements. and an electronics unit inside the Rus- are partially outside the space station sian service module, the space cap- in the orbit vacuum, which makes them sule, where the experiments are con- rather difficult to check. ducted. The electronics unit contains a highly stable crystal oscillator, transmit- When an onboard multimeter was used, ters for the UHF and L band and a con- only short circuits or cable breaks were troller which generates the transmis- able to be eliminated as possible causes sion signals via software in realtime. of deviation. To measure the RF charac- This unit is directly controlled and mea- teristics, it was thus crucial to procure a sured from a special ground station in lightweight mobile device that offered Stuttgart; otherwise, the controller func- battery operation and could be remote- tions autonomously. It also ensures cor- controlled via a laptop – in other words, rect antenna control which compensates an instrument such as the Handheld the significant differences in free-space Spectrum Analyzer R&S ® FSH3. Since attenuation between the nadir and hori- laptops are part of the basic equipment zon direction by means of a specially on board the space station, “all” that designed directional pattern. needed to be done was to transport the 2 kg analyzer to the space station: With The antenna was installed in Moscow each kilogram costing US$ 20000, every in December 1998 before the service gram counts! module was launched. In summer 2000, the electronics unit was delivered by

28 News from Rohde & Schwarz Number 184 (2004/IV) oto: NASA Ph

FIG 3 Cosmonaut Deschurow installs the electronics unit for the GTS system.

FIG 2 A joint project involving several countries: The International Space Station ISS is a manned science lab in space. NASA oto: Ph

29 News from Rohde & Schwarz Number 184 (2004/IV) GENERAL PURPOSE Reference

Moreover, a number of questions had to ies were removed and replaced by a spe- it was handed over to the Russian part- be clarified: Would the R&S ® FSH3 with- cial power supply for matching the ISS ner company RSC Energia, which trans- stand the extreme stress it is subjected power supply. Finally, the interior fac- ported it together with the Progress cap- to when being transported into orbit? ings of the housing were completely cov- sule to the ISS in February 2004. Would its electronics work even under ered with self-adhesive aluminum foil to the increased radiation exposure at an meet fire protection requirements. Thus In the meantime, the procedure for altitude of 400 km? Would the spectrum modified, the R&S ® FSH3 once again installing the R&S ® FSH View software analyzer meet the ISS security require- immediately functioned without any and for performing the measurements ments so that it would neither endan- problems even though the firmware had had been transmitted to the ISS crew. ger the crew nor interfere with onboard not been designed for operation without The big day finally came on 18 March: electronics? The most important and rechargeable batteries (FIG 4). The R&S ® FSH3 was installed and was pressing question, however, was: Would ready to perform its first measurements the R&S ® FSH3 be able to accurately (FIG 5). measure the cables which are almost Thoroughly tested 30 m in length and outfitted with various connectors, or is the cable loss too high? The next challenge the R&S ® FSH3 had A shooting star to face were mechanical vibration tests. To answer these questions, the entire Again, the analyzer excelled because the As expected, the R&S ® FSH3 functioned setup was simulated in Moscow with quality standards at Rohde & Schwarz smoothly despite the increase in radia- the aid of the phantom flight antenna are so demanding that no further tion exposure. The measured data was model and the ground simulator of the mechanical tests were necessary. When transferred from the spectrum analyzer service module. The R&S ® FSH3 was EMC and radiated emission were tested, to the ISS telemetry system via laptop set to distance-to-fault measurement the values measured were minimal and and transmitted to the ground station for mode, and the cables were tested. The not significant enough to jeopardize the evaluation on 22 March 2004. The dis- measurement was a complete success: electronics on board the ISS. Thus, no tance-to-fault measurement revealed Despite the considerable cable lengths, further shielding was necessary. everything: The discontinuities of the the spectrum analyzer was able to dis- cable connections were clearly visible, play even the delay differences between Finally, thermal and vacuum tests had as were two other spikes in the diagram the phase shifter elements in the active to be performed because such excep- that could not be replicated during the antenna and thus passed this first test tional stress does not occur when the ground simulation (FIG 6). These inter- for such an unusually sophisticated R&S ® FSH3 is used on earth. The spec- ferences seem to be at least part of application with flying colors. trum analyzer was subjected to a tem- the reason for the reduced signal qual- perature range of –50 °C to +50 °C ity and are currently being analyzed in a climatic chamber, simulating the in detail. Until final clarification, the Off to the “gym” extreme conditions that can occur R&S ® FSH3 will remain on board the ISS. during launch from Russia’s Baikonur Then it will be sent back on a Progress Next, the R&S ® FSH3 had to be prepared space center. Since a pressure loss transporter only to burn up as a shooting for launch and for operation on the might also occur in the Progress trans- star when reentering the earth’s atmo- space station. As is usual with commer- port capsule, the instrument had to sphere. cial off-the-shelf (COTS) products, the pass the corresponding tests. The Dr Felix Huber safety experts completely dismantled the R&S ® FSH3 easily withstood vacuums up (Steinbeis Transfer Center instrument and subjected it to a thor- to 400 mbar in a tank. for Space Travel) ough inspection. In particular, materials containing PVC and electrolytic capac- To ensure that the instrument would itors might endanger the astronauts not emit any toxic substances, it was and must therefore be replaced. How- wrapped in polyethylene foam rubber ever, since there was no viable alterna- and subjected to an outgassing test in tive for the capacitors in the switching a high-temperature-resistant bag for power supply, they were encapsulated 72 hours. The spectrum analyzer excelled in Teflon sleeves together with absor- once again and was finally granted bent material. The rechargeable batter- launch permission. In December 2003,

30 News from Rohde & Schwarz Number 184 (2004/IV) FIG 5 After strenuous tests and a long journey, the R&S ® FSH3 finally reached the ISS, where measurements then began. RSCE oto: Ph TZ Raumfahrt oto: Ph

FIG 4 Ready for a trip to space: the R&S ® FSH3 after modification. Especially materials containing PVC and electrolytic capacitors could endanger the astronauts and thus had to be replaced.

FIG 6 Results of the DTF measurement: cable discontinuity (marker D1); unwanted faults (marker D2 and D4); duct from space station to the antenna outside (marker D3); antenna (marker D5).

More information and data sheet at www.rohde-schwarz.com (search term: FSH3)

REFERENCES [*] Handheld Spectrum Analyzer R&S ® FSH3: Numerous expansions and a new model. News from Rohde & Schwarz (2004) No. 181, pp 32–35

31 News from Rohde & Schwarz Number 184 (2004/IV)