The International Ultraviolet Explorer (IUE)
IUE has been in continuous operation as joint project by NASA, ESA and the United Kingdom (initially SRC, later SERC, and now PPARC) since the satellite's launch on 28 January 1978, the ESA IUE Observatory being located throughout at the Agency's Villafranca Satellite Tracking Station (VILSPA) near Madrid (E). Following the approval of a new 'hybrid operations scheme' by ESA's Science Programme Committee (SPC) in May 1995, the necessary developments were carried out over the summer months to allow this new operating scheme to start on 1 October 1995.
The International Ultraviolet Explorer (IUE)
Under this revised 'hybrid' system, the total observing time (previously 24 h) has been restricted to the 16 h per day when IUE is outside the influence of the Earth's radiation belts. During this 16 h observing period, both the spacecraft and science operations are under VILSPA's control. For the remaining 8 h each day, the spacecraft is controlled from NASA's Goddard Space Flight Center (GSFC) in Greenbelt MD.
A number of additional activities were needed to assure a timely implementation of the hybrid operations, namely:
In the event, it assigned 9500 h of observing time, maintaining some 1500 h in reserve, and 14 proposals were given 'lasting value' (i.e. key programme) status.
Spacecraft status
A new anomaly is affecting one
of the S-band downlink antennas (no. 4) which has had
intermittent problems in the past; its output has now decreased
permanently by 30%. Analysis suggests that this is caused by a
failure in the amplification chain, whereby only one of the
original two amplification chains remains operational. The impact
on operations is limited since it corresponds to only a 15%
decrease in the useful antenna pattern as seen from the ground.
Occasionally, however, the spacecraft may have to be reoriented
for data transmission.
Scientific highlights
The first observations of
Comet Hale-Bopp have been successfully completed. Even though
some solar background contamination is present in the spectrum,
the continuum of the comet was well detected and suggests one of
the largest dust-production rates ever observed; no water
evaporation (as manifested by OH emission) was found at a
relatively high upper limit of 1E29 mol/s. A dark, icy spherical
nucleus would yield this evaporation, if it had a radius of some
400 km.
The reverberation campaign on the high-luminosity Seyfert-1 galaxy F-9 has been completed and shows considerably shorter emission-line delays with respect to the continuum variations than the 400 days anticipated from previous results for this galaxy.
Archiving
The processing of the VILSPA data for the
IUE Final Data Archive (IUEFA) has continued in parallel with the
innovations that were introduced in connection with the hybrid
operations. The IUEFA distribution system, which is expected to
support the long-term usage of the IUE Archives, is in its final
design stages.
The HST Observatory continues to operate with excellent efficiency, with only minor malfunctions with no impact on the scientific operations reported in recent months. By the deadline of mid-September for the submission of proposals for the next observing cycle (Cycle 6), more than 1000 proposals had been received.
'Gaseous pillars' in the Eagle Nebula, imaged by HST
The preparation and planning for the 1997 Maintenance and Repair Mission is proceeding on schedule. During that mission, two new instruments -the ST Imaging Spectrograph (STIS) and Near- Infrared Camera (NIC) -and a Fine Guidance System (FGS) unit will be installed, together with a number of subsystems which need replacement. The current planning envisages 6 h of Extra- Vehicular Activity (EVA) on four consecutive days, plus an unscheduled EVA as a contingency.
Together with the Space Telescope Science Institute, the ST European Coordination Facility (ST-ECF) is involved in the preparations for the 1997 Servicing Mission. This includes participation in the activities of the ScI Servicing Mission Office and, in particular, support for advanced calibration and data-analysis procedures for the next-generation science instruments (STIS and NIC). This work will be based on the existing experience with image restoration and with similar work performed by the ST-ECF for the Faint Object Spectrograph.
Scientific highlights
The most recent scientific
highlights include observations of Solar System objects
(resolving the surface of Vesta, discovering moons of Saturn),
mapping objects of embryonic stars, and the discovery of large
numbers of irregular and peculiar galaxies at large distances.
These will be followed up with the 'Hubble Deep Field' project,
which is designed to provide an ultra-deep exposure of the
highest possible resolution. The ST-ECF's contribution to the
latter project consists of the development of techniques for the
pixel sub-stepping and image recombination.
Many of these results, as well as up-to-date information about HST and the ST-ECF, can be found on Internet via WWW address:
http://ecf.hq.eso.org/ST-ECF-homepage. html
Archiving
Several important archive-related
activities have taken place recently. The ST-ECF HST Archive has
been adapted to the new format and optical-disk standard of the
new Data Archive and Distribution System (DADS). In addition, the
new User Interface developed by the ST-ECF, based on the World
Wide Web (WWW) protocol and available on Internet, has
considerably improved accessibility to HST data. The positive
effect of the new interface has been clearly visible in increased
use of the Archive during the first three quarters of 1995.
Mission and spacecraft status
On 30 September 1995,
five years after launch, Ulysses completed the first phase of its
highly successful exploratory mission to study the Sun's
environment from the unique perspective of a solar polar orbit.
Between 19 June and 29 September, one year after its historic
south polar pass, the spacecraft flew over the Sun's northern
polar regions, reaching a maximum latitude of 80.2 degrees north
of the equator on 31 July. The mission continues to go well, with
all spacecraft subsystems and scientific instruments functioning
nominally.
Ulysses
In retrospect, the first five years of the Ulysses mission have covered many ground-breaking activities from an operational standpoint. The launch in October 1990 was the first occasion on which ESA staff were operationally responsible for a Shuttle payload during an eventful 6 h period which culminated in the spacecraft's successful deployment and the start of its journey to Jupiter. The unexpected onset of nutation shortly after deployment of the spacecraft's axial boom presented a further challenge in terms of analysing and understanding the causes of the anomaly. Correct interpretation enabled preparations for the expected return of nutation in 1994 to be carried out in an orderly manner, allowing its successful control during a period of over one year. These activities stretched to the limit the NASA and ESA ground facilities used for the task, as well as the operational staff located at JPL and at the ground stations. The fact that the scientific data acquired were not degraded is proof of the success of these operations.
The encounter with Jupiter in February 1992 was also a first for ESA operations staff and presented many challenges. A unique method of conducting the operations was devised which provided the experiment teams with the ability to access their experiments in near-real-time during the actual encounter. Looking ahead, science data-gathering activities will continue throughout the entire second solar orbit, no doubt leading to new operational challenges.
Scientific highlights
Highlights from the out-of-
ecliptic, in-ecliptic and Jupiter fly-by parts of the prime
Ulysses mission to date are listed in the accompanying panels.
Although the list is by necessity not exhaustive, it serves to
illustrate the richness and diversity of the scientific harvest
from the mission so far. Almost without exception, the most
important results have come from the analysis and interpretation
of combined data sets from different instruments, a natural
consequence of the high degree of integration and collaboration
within the Ulysses science team.
More than 400 papers discussing these and many other findings from the Ulysses mission have been published since launch, including seven collections of papers in special issues of scientific journals. An eighth is currently in press in Geophysical Research Letters, and it is planned to publish the results from the North Polar Pass Workshop, held in California last October, in a special issue of 'Astronomy and Astrophysics'.
Ulysses' second solar orbit
With the spacecraft and
its scientific payload in excellent condition, Ulysses is all set
to embark on its second orbit of the Sun. The ultimate goal of
this next phase of the mission is the study of the Sun's polar
regions under conditions of high solar activity, culminating in
polar passes in 2000 and 2001. Much before this, however, as
Ulysses descends slowly in latitude after the northern polar
pass, there will be a unique opportunity to make coordinated
observations with ESA's SOHO spacecraft, which carries an
extensive complement of experiments dedicated to studying the
Sun's corona and the solar wind. The period around aphelion
(1997/98) will also be of great interest. During this interval,
Ulysses will spend many months close to the ecliptic at almost
constant radial distance (some 5 AU) from the Sun, enabling the
temporal evolution of many interplanetary phenomena to be studied
free of concern about spatial variations.
Ulysses is clearly in a unique position, literally and figuratively, to study the evolution of the three-dimensional heliosphere from the current solar minimum to maximum activity conditions. No other space mission in the foreseeable future will address these goals.
The control of all Meteosat spacecraft in orbit was transferred to Eumetsat at the end of November. The primary imaging service is currently being provided by Meteosat-5, with Meteosat-6 on stand-by.
The MOP (Meteosat Operational Programme) design will be used for yet one more spacecraft, to be known as the Meteosat Transition Programme (MTP) satellite. Its radiometer is currently being manufactured and will be delivered in early summer 1996. Launch of the MTP spacecraft is planned for summer 1997.
The Infrared Space Observatory was launched successfully at the opening of the daily launch window at 01.42 h UT on 17 November 1995. The launch sequence proceeded smoothly, exactly to schedule and orbit insertion was extremely precise.
The ISO spacecraft, just prior to launch
During the first four days after launch, covering the Launch and Early Orbit Phase (LEOP), the satellite was controlled from the ESA Flight Operations Centre at ESOC, in Darmstadt (D). The health of the satellite's subsystems was checked and then the perigee altitude was raised from 518 to 1030 km. During the subsequent Commissioning Phase between 21 November and 8 December, the satellite, with its scientific instruments, was controlled from the ESA Mission Control Centre at Villafranca, near Madrid (E). All satellite subsystems were successfully tested and commissioned during this phase. The apogee altitude was adjusted to achieve the final orbit of 24 h period (70 611 km apogee and 1004 km perigee). The cryostat cover was ejected 10 days after launch and all scientific instruments have since been tested and have been making observations of various objects in space. Both the satellite and the scientific instruments are performing extremely well.
All flight operations and the ground segment, including the two ground stations at Villafranca (E) and at Goldstone (USA) are also working extremely well.
The Observatory Performance Verification Phase, during which the scientific instruments will be thoroughly characterised and calibrated and all critical automatic sequences tested, began on 9 December.It is planned to start the Routine Operations Phase in early February 1996.
The system-level Critical Design Review process reached a climax with the meeting of the Review Board, chaired by ESA's Director of Scientific Programmes, R. Bonnet, and ESA's Inspector General, M. Trella, at ESTEC on 12 October.
The majority of the small number of issues needing the Board's attention resulted in actions of a more or less 'normal work' type, but two issues were highlighted for particular attention. Problems identified during the so-called 'Titan Entry Test', or low-temperature pressurised-atmosphere test, necessitated further study of the behaviour of the Probe's insulating foam.
The effects of pyrotechnic shocks upon electrical units were also deemed to require further examination. Study contracts to examine these two areas have therefore been let to specialist organisations, whose findings are due to be reported by the end of 1995.
Integration of the flight-model Probe continues at DASA (D). Some delayed deliveries of Probe hardware have necessitated work- around solutions, but integration in general has not been held up.
Delivery for integration of the flight-model experiments is deviating somewhat from the nominal plan and the resulting work- around solutions and erosion of contingencies has put pressure on the overall schedule. However, the Probe's delivery date to the launch site is not endangered.
The first part of the industrial design phase (Phase strong) has been concluded with the System Requirements Review, with the Board meeting on 18 December. This review confirmed the concept of commonality of the Integral Service Module with that being developed for XMM. The Review also clearly identified key system- level points that require special emphasis at the start of the second part of Phase strong.
Payload instrument design by the scientific collaborations is proceeding in parallel with the spacecraft development. Instrument system design has converged to a point where the spacecraft configuration and electrical architecture can be frozen.
The work on the interface with the Proton launcher is progressing slowly, still being hampered by the lack of a formal ESA/RKA Arrangement for Integral.
All of the ERS-2 instruments and the spacecraft platform continue to operate nominally.
The satellite performances remain very good and similar to those of ERS-1, making possible the unique nine-month ERS-1/ERS-2 Tandem Operation phase, which started in September. The main objective is to perform interferometric imaging of the land surface on a global basis leading to, among other important goals, a quasi-global digital terrain map.
The Scatterometer investigation campaign was successfully concluded at the end of November with the development of a work- around for the technical anomaly and the achievement of a stable operational approach. Although data quality and long-term stability are still under evaluation, the chances of the ERS-2 instrument achieving full operational status now look very good.
The commissioning of the ERS-2 Scatterometer which was delayed during the trouble-shooting will start in January 1996 and last for three months.
The ERS-2 Commissioning Phase review, covering all of the instruments as well as the ESA ground segment, took place in October. With the exception of the Scatterometer, all other elements of the system were confirmed as operating nominally.
The recurrent (from ERS-1) instruments - SAR, RA and MWR - could be declared operational: the 'new' instruments - GOME, PRARE and ATSR-2 - were still in the first stages of commissioning, although very promising results were already available, confirming the high expectations. Release of data from these instruments will be authorised at the beginning of 1996.
Future programmes
Following the establishment of
an agreed mechanism and procedure for the selection of first-
priority Earth Explorer missions, the major activity during the
reporting period has been to initiate all activities appropriate
to the production of assessment reports on each of the nine
candidate missions to support the selection of the missions to
proceed to Phase-A.
The future extension of EOPP beyond mid-1996 is still being discussed with Delegations.
Campaigns
While the analysis of data from previous
campaigns continues - particularly the EliTE campaign which is
expected to improve our fundamental understanding of backscatter
lidar design - work has proceeded on defining future campaigns.
Envisat-1 payload
All instrument negotiations, with
the exception of those for ASAR, have now been completed.
Delivery dates have been agreed which are consistent with a mid-
1999 launch. Most ASAR subsystem contracts have also been
negotiated. The ASAR instrument contract negotiation, and that
with the mission prime contractor, will be completed in early
1996.
Structural models of MIPAS and the SCIAMACHY Optics Assembly have been delivered to the Polar Platform prime contractor. Other structural models, including ASAR, will complete their mechanical test programme and be delivered in early 1996.
Manufacture of engineering-model subsystems continues in accordance with negotiated schedules, with deliveries due in many cases in the first quarter of 1996. Integration of the engineering-model AATSR instrument is nearing completion, as are all the electronic subsystems of SCIAMACHY.
The withdrawal by CNES of the ScaRaB radiation-balance instrument and its associated shared Instrument Control Unit has necessitated some technical reconfiguration.
Manufacture has started of a number of elements of the Flight Model Instrument structure. A number of associated low level Critical Design Reviews have been held. On 9 November, a detailed presentation of the technical status of the Envisat Programme was made to the delegates of the Data Operations Scientific and
Technical Advisory Group of the Agency's Earth Observation Programme Board. The DOSTAG concluded that 'a solid technical baseline existed for the Programme'.
Detailed investigations have been made into cost-saving measures which could be applied to the baseline programme. These measures are being investigated in parallel with the ongoing technical work. Conclusions in this area are expected in early 1996.
Polar Platform
Activities are proceeding as
planned. The static load test of the PPF structure has been
completed. Good correlation was achieved with predictions and the
structure was submitted to the maximum loads currently predicted
for the Ariane-5 environment and the latest payload mass
distribution. The proto-flight structure has been delivered by
CASA (E) to MMS-strong (strong) for structural-model integration.
Structural-model tests are planned to start at the end of March
at ESTEC (NL).
For the Critical Design Review (CDR) for the service module has been completed successfully and electrical integration has started.
The Payload Electronics Bay (PEB) electrical integration is in progress. Acceptance testing is scheduled for the first quarter of 1996, followed by the PEB's CDR and delivery to the prime contractor.
Envisat-1 ground segment
The Payload Data Segment
(PDS) development activities were kicked-off with the prime
contractor, Thomson-CSF (F), in early October.
The METOP design phase (Phase-strong), kicked-off in July 1995, has progressed up to the Preliminary Review, which is planned for completion in January 1996.
Due to uncertainties in the definition of the main development (Phase-C/D) programme, it has proved necessary to interrupt the Phase-strong activities until a consensus can be found. Accordingly a 'holding' phase of two months has been introduced which will then permit a re-direction of the industrial activities, with minimum impact, up to mid-February 1996.
The other activities within the METOP Preparatory Programme are progressing well, with the ASCAT instrument demonstrator nearing the end of its integration and the MIME demonstrator having started this phase.
Further meetings of Potential Participants and of EUMETSAT regarding the METOP-1 Phase-C/D programme and the EUMETSAT Polar System programme have been held and more are planned. A consolidation of the baseline programme has not yet been agreed and a radically descoped programme is being considered.
The main development phase (Phase-C/D) has been proceeding on schedule, with a successful Baseline System Review being held in mid-October 1995. A series of lower-level preliminary design reviews follows, with the main objective of releasing engineering-model manufacture and thermal/mechanical-model manufacture at equipment and subsystem level.
The MSG optical instrument SEVIRI (Scanning Enhanced Visible and
Infra-Red Imager)
For the MSG-2 and 3 recurrent models, the Eumetsat Council, at its November session, approved in principle their financing by Eumetsat and their procurement from industry by ESA as Eumetsat's procurement agent.
With ESA's MSG-1 to be launched in mid 2000, and MSG-2 in the year 2002 for in-orbit standby to MSG-1, the spacecraft development and manufacturing programme now extends until 2003, the year in which MSG-3 will be placed into ground storage nominally for five years. This scenario is needed by Eumetsat to guarantee an uninterrupted operational geostationary imaging and data dissemination service from the year 2000 until 2012, each spacecraft having a design lifetime of seven years.
European contribution to International Space Station Alpha
(ISSA)
Following the adoption of the Declaration on the
Manned Space Programme at the ESA Council Meeting at Ministerial
Level in Toulouse (F) in October, the planning for the initiation
of the new programme elements was reviewed to ensure a smooth
transition from the approved ongoing programme slices.
Columbus Orbital Facility (COF)
The primary
emphasis in the technical area focussed on closing out the
remaining technical non-compliances against the ESA/NASA joint
requirements baseline. Some detailed design aspects of the
COF/ISSA interface were addressed in a multi-lateral
International Interface Working Group meeting between ESA, NASA
and NASDA in Houston during the last two weeks of October, where
all Interface Control Documents involving the COF were reviewed
and updated in line with the latest ISSA baseline.
In the programmatics area, the primary emphasis was directed towards adaptation of the overall development schedule to take into account the shifting of the COF launch from February to November 2002 within the overall funding and payment profile constraints as defined by the Programme Proposal.
MSTP Technology Programme
The programme has
continued with studies and technology experiments concentrating
on:
Atmospheric Re-entry Demonstrator (ARD)
The failure
of the ARD drop test was a disappointment and various alternative
means and tests necessary for parachute qualification were
reviewed. It was concluded that a drop test with a representative
mockup from a balloon was the only test that would allow full
qualification of the parachute in the appropriate flight domain,
and so a further test will be scheduled in the spring of 1996.
Automated Transfer Vehicle (ATV)
Following the
System Requirements Review, the system specifications, element
architecture and project plans were consolidated. The re-boost/
refuelling/pressurised cargo mission to the Russian segment of
the Space Station, which is the baseline mission in the Programme
Proposal, will be further studied in the January-May 1996 Phase-strong
extension with Russian and European contractors.
The ATV preparatory activities continued, with emphasis on the interfaces between the kernel, sensors and receivers for the US Global Positioning Satellite System (GPS). The first GPS receiver development model was prepared for system tests, while manufacture of the rendezvous laser sensor development model was authorised. The ARP kernel activities continued to focus on the preparation of the in-flight demonstrations with the NASA Space Transportation System and interfaces with the ATV programme.
Crew Transportation Vehicle (CTV)
The Phase-A
extension activities undertaken by industry have concentrated on
a single vehicle concept. It comprises a launch escape tower, a
crew module, and a dedicated resource/propulsion module
integrating additional room for possible use of launch margins.
The CTV precursor to be used for the orbital flight test in 2002
was also analysed in parallel.
Early deliveries
Columbus Mission Database (MDB)
The pre-delivery review for the final MDB delivery to
NASA/Boeing under ESA's Early Delivery obligation was
successfully completed in Bremen.
Core Data Management System for the Service Module (DMS-R)
An extensive series of technical interchange meetings with
European and Russian industry and the Russian Space Agency (RSA)
were completed in Moscow during October. These meetings produced
considerable progress in defining the detailed DMS-R technical
baseline, including all interfaces to the Russian segment.
European Robotic Arm (ERA)
Industrial work proceeded and
the first of the Subsystem Preliminary Design Reviews was
initiated. These reviews, which serve to formally release the
manufacture of the ERA qualification models, will conclude with
a system-level Programme Design Review in the first quarter of
1996.
Environmental Control and Life-Support System for the Italian
Mini Pressurised Logistics Module (MPLM ECLS)
Following
finalisation of the Cooperative Arrangement between the Italian
Space Agency (ASI) and ESA, the industrial tasks were formally
initiated. Meetings were held with industry, ASI and the MPLM
prime contractor to review the overall programme schedule in
order to avoid any delay in the planned MPLM launch dates.
Laboratory Support Equipment
Utilisation
A meeting on 'Space Station Utilisation
for Technology' took place at ESTEC in November to discuss
technology projects, technology user requirements, and access
conditions to the Space Station for European projects. This
meeting was complemented by a Workshop organised by ESA's Office
of Space Commercialisation to review the activities of the
different RADIUS (Research Associations for the Development of
Industrial Use of Space) members and to discuss opportunities for
future access to space for commercial users.
The Euromir 95 mission, with the ESA astronaut Thomas Reiter on board the Russian space station Mir, is progressing as planned. Up to now, the overall experimental programme (life sciences, astrophysics, material sciences, technology) has been kept very close to schedule, with no major interruptions or failures. A total of 41 experiments are being carried out during the 180-day mission, which is now scheduled to end on 29 February 1996.
ESA Astronaut Thomas Reiter at work aboard Euromir 95
The major highlight of the mission to date has been the 5 h Extra-Vehicular Activity (EVA) of Thomas Reiter and his Russian colleague Sergei Avdeev on 20 October, during which elements of the European Science Exposure Facility (ESEF) were successfully deployed outside the Spektr module. Another highlight was the three-day docking of the US Space Shuttle 'Atlantis' with Mir in November. This was the first time American, Canadian and European astronauts and Russian cosmonauts had worked together aboard a space station, making it something of a preview for the International Space Station.
All of Thomas Reiter's activities are planned at and monitored from DLR's German Space Operations Centre in Oberpfaffenhofen. The mission management team is located at ESTEC in Noordwijk (NL), and an operations support team at the ZUP Russian Control Centre in Kaliningrad, near Moscow, interfaces directly with the Russian flight authorities.
A further programme covering the development of microgravity multi-user facilities for the Space Station was approved at the ESA Council Meeting at Ministerial Level in Toulouse in October. A subscription level of 98.03% of the overall financial envelope of 202 MAU was achieved for this 'Microgravity Facilities for Columbus' (MFC) programme.
The USML-2 Spacelab mission took place from 20 October to 5 November. The two ESA microgravity payloads on board -the Advanced Protein Crystallisation Facility (APCF) and the Advanced Glove Box - both performed very well and the results of the various experiments are currently being evaluated.
The Maxus-2 sounding rocket, providing 12 min of weightless conditions, was successfully launched from Kiruna on 28 November. Four fluid-physics and four life-sciences experiments were conducted. One experiment gave only partial results due to a mechanical malfunction, but the other seven were completely successful.
The Maxus-2 launch from Kiruna (s) on 28 November
ESA Bulletin Nr. 85.