[Space] ESA - Rosetta Comet Chaser - Update Thread

[Ser21]

Originariamente inviato da baldoz
Vero
L'Italia (come ASI, Agenzia Spaziale Italiana) ha partecipato a Rosetta con l'SD2 di progettazione Tecnospazio S.p.A. (Galileo Avionica).
In pratica si tratta del "trapano" che effettuerà il buco sulla cometa per poi analizzarne i gas.

Alcuni dirigenti di Tecnospazio sono stati inviati alla sede dell'ESA nei Paesi Bassi per seguire da vicino le ultime fasi di preparazione prima del lancio.

Inoltre una collega di mio padre era a Kurou per assistere al lancio (in primavera 2003... poi rimandato a questa settimana).

M-I-T-I-C-O grazie x il contributo

[GioFX]

Originariamente inviato da baldoz
Alenia si occupa di altro, comunque il gruppo è sempre Finmeccanica.

Lo so, si è occupata dell'assemblaggio.

[Thunder82]

.

[Thunder82]

.

[Thunder82]

.

[Thunder82]

Sono contento che il lancio sia andato bene!
Io faccio Ing. Aerospaziale qui a Padova. La facoltà è stata istituita da 3 anni, per rendere omaggio al Grande "Bepi" Colombo, professore ormai deceduto 20 anni fa dell'università di Padova che ha dato importantissimi contributi alla NASA nel campo della propulsione e la gestione dei veicoli spaziali (talmente importanti che la NASA gli dedicherà una sonda mi pare, è la prima volta che chiamano una sonda col nome di una persona...).

Volevo anche dire che il CISAS di Padova (il cui presidente è il mio professore di misurazione e metrologia generale meccanica ) ha avuto un ruolo estremamente attivo nella progettazione della Wide Angle Camera a bordo di Rosetta (solo questa "videocamera" è costata la "sciocchezza" di 3,6 milioni di dollari...) ed ha anche progettato il PFS (Planetary Fourier Spectrometer) che era stato montato sulla nave madre di Beagle2 e che ha scoperto l'acqua ghiacciata al polo sud di Marte.
Inoltre l'università di padova sta eseguendo studi molto avanzati su impatti ad ipervelocità con detriti spaziali (di cui ormai le orbite sono piene) con un cannone a ipervelocità da 7km/s!

Questo per dire che l'Italia è in una posizione veramente di primo piano nella ricerca spaziale, e posso solo esserne contento visto che (spero) sarà il mio lavoro!

BUONA FORTUNA E BUON VIAGGIO ROSETTA!

[Thunder82]

ma che ha il forum stasera? mi ha fatto fare 5 post uguali...

[Thunder82]

Ecco la wide angle camera montata su Rosetta



E il planetary fourier spectrometer su mars express:







The Wide Angle Camera for the OSIRIS system of the cometary mission ROSETTA (P.I. of Osiris is Dr. U. Keller, MPAe) is characterized by an innovative two mirror optics (the primary being convex), large FoV (12x12 deg) and extremely clean PSF in order to detect faint gaseous features close to the bright cometary nucleus.

The scientific activity is done inside the Dept. of Astronomy (prof. C. Barbieri) and Astronomical Observatory.

The hardware activity (optical bench, thermal control, baffle, shutter, front cover, etc.), is supported by CISAS through the Depts. of Mechanical Engineering (Prof. F. Angrilli) and Electronics and Informatics (Prof. G. Tondello). Other collaborators are from the University of Venice (Prof. P.F. Brunello) for the baffle optical design.

The main scientific goals of OSIRIS as a whole were identified from the present large ignorance on the physical and chemical state of the surface of a cometary nucleus.
It is planned to obtain data on topography, morphology, layering, inner structure, number and location of active regions, rotation of the body, emission processes of dust and gases.
Erosion can be measured with images having resolution of 10 cm.
Global mapping at better than 1 m/px can determine the 3-D structure, density to better than 1% and moments of inertia (in cooperation with radio science).

For the dust, it is planned to obtain the column density just above the surface, and to detect its emission at large heliocentric distances. Structures in the dust coma could change over short time intervals, so images are needed with rapid repetition rates. Day/night effects can be detected observing eclipses in forward scattering.

Regarding cometary gases, the cancellation of the IR channel and of the UV capability had the consequence of preventing a large scientific body of investigations on the parent molecules (like water) from being carried out with OSIRIS. Therefore only daughter molecules will in general be followed near the nucleus surface and in the coma. High speed monitoring will be carried out also in the gas filters.

Secondary scientific targets of OSIRIS are the two asteroids that will be encountered during the flight to the comet, at the moment Otawara and Siwa.

Specific Objectives for the WAC

Asteroids

The two target asteroids are (to be confirmed):

a) 4979 Otawara, H=14.3, encounter 10 July 2006, flyby velocity = 10.6 km/s,
Sun-asteroid-S/C angle at approach = 31 deg, distance to Sun at encounter = 1.7 AU (X=-0.8, Y=-1.7), distance to Earth at encounter = ..., minimum distance S/C - asteroid = 1000 km (TBC)

According to information provided by N.Thomas (30 Nov. 98), the centre coordinates of the background stellar field as seen by the S/C are: 14h00m, -22deg0'.

b) 140 Siwa, H=8.3, encounter 23 July 2008, flyby velocity = 17.0 km/s, Sun-asteroid-S/C angle at approach = 12 deg, distance to Sun at encounter = 2.6 AU (X=-2-6, Y=-1.0), distance to Earth at encounter = ..., minimum distance S/C - asteroid = 1000 km (TBC) According to N.Thomas (30 Nov.1998) the coordinates of the center stellar background as seen by the S/C are: 12h32m, -02deg00'.

The main scientific goals of WAC camera during asteroid fly-byes are:

to contribute to the astrometric studies, using the rich stellar background
to ascertain its environment, such as a possible satellite or dust coma
to characterize the body (size, shape, pole orientation, period of rotation, density) and surface (cratering and mineralogical composition) producing a multi-band albedo map
A satellite of an asteroid is expected (from dynamical and statistical considerations) to orbit within one or very few hundreds of the parent asteroid radius.
140 Siwa is a large asteroid, with a diameter estimatd from 115 to 150 km. Some authors (Schober and Stanzel 1979; Harris and Young 1980) give a rotation period of >22 h; Lagerqvist et al. (1992) estimate instead 18.5 h. Our group (see Barucci et al.,1998) has obtained 8 spectra of it. The tassonomic class is C.

4979 Otawara is small, 10 to 20 km, and essentially unknown.

Siwa then drives the requirements for the total field to be surveyed for a companion. In order to image a field of some 3.4x10^5 km with the 12 deg field of the WAC the first images must be taken from a distance of not more than 10^5 km: at that distance the resolution is of 10 km/px, and Siwa occupies on the CCD some 10x10px. Exposure times ranging from 10ms to 100ms can be utilized without incurring in saturation problems (to be refined). From this distance onward, the saturation will not change (constant surface brightness), but the asteroid will be increasingly resolved. In 100ms we obtain a good S/N ratio with 5th mag stars or brighter.
Regarding the surface characterization, at the expected approach distance of 1000 to 1500 km, the NAC FoV will image only part of the surface of Siwa (40x40 km to 60x60 km). Therefore we have to take images with both cameras.

Activities of the WAC Team:

a) Ground and Space Support: to collect images and spectra of the targets and of other similar asteroids to improve the knowledge of the main physical and mineralogical characteristics.
b) Modeling: we plan to model the shape and rotational state of the asteroid, using techniques such as photo-clinometry.

Cometary Physics: Our team plans to observe the comet during the entire mission.

Cometary Nucleus Main contributions of the WAC will be:

to help with recovery and astrometry in respect to the stellar background
to help to time the starting of cometary activity
to perform a global analysis to determine the overall shape, dimensions and rotational status.
to survey large scale features in order to identify the shape and number of the supposed cometary building blocks (whose sizes could range from 10m to 100 m, although most theories favour larger sizes from 100m to 600 m)
to contribute to produce a multi-band albedo map to determine global surface composition, texture, and porosity
to provide the reference frame for NAC images and Surface Science Package Roland landing site. Maximum exposure times of 100 msec during global mapping are set by smearing.

To provide mapping of large areas at very close distances, the WAC must stay in acceptable focus down to better than 1 km from the comet.

Dust Coma Main goals are:

to map the distribution of dust around the nucleus, to identify jets, streamers, etc.
to determine the dust production rate, dust size distribution and dust velocity (in conjunction with GIADA measurements).
According to current models, the dust particle velocity could range between 0.5 and 1 km/s, which is the gas drag velocity. However ISO data on comet Wirtanen give a much smaller velocity of 25 m/s for 0.1mm particles 120 days before perihelion. A better determination of this dust particle velocity will be greatly helped by the WAC images. In order to observe dust structures in the near vicinity of the surface, a very high contrast ratio is needed, at least 10^{-4} as the ratio between the nucleus and the dust features brightness. To reach this high contrast ratio is one of the main drivers for the WAC optical design.
Gas Coma

The WAC images will be used to determine the gas production rate, distribution and velocity. To perform this topic we need to collect images already during the approaching phase, at about 3.3 AU from the Sun; in this way it will be possible to detect the presence of activity (possibly even a fossil coma) at such large heliocentric distances, as for example of the CO and of other radicals.

During the approach to the Sun, the WAC will take images in the gaseous band filters, in particular of the OH, of the CS (in the near UV, where no other instrument can observe), and of the Na. The Giotto mission found a collisional coma of about 3000 km for the comet P/Halley; considering that comet P/Wirtanen is less active than P/Halley, we need to get images at a distances not lesser than 7000 km from the nucleus. The discovery of the Na tail on comet Hale-Bopp raised a great deal of attention on NA production and distribution. Different sources seem to at work, such as release of gases from the dust particles, molecular dissociations, release directly from the nucleus.

Activities of WAC group:

to model the nucleus adopting the photoclinometric method
to improve the hydro-dynamical model of the coma considering the physical and dynamical properties of the dust particles
to model the distribution of the gas around the nucleus and the active regions on the surface.
Ground Support:
photometric observations of the coma and of the dust tail of the comet P/Wirtanen and other short period comets (P < 20 years).
Mission Phases: Asteroid Fly-byes

a) Otawara. Given the small dimension of the asteroid, the NAC can perform most of the scientific goals. However the larger FoV of the WAC gives a richer stellar background.

b) Siwa. For the detection of the possible satellite the WAC needs to take images starting from at least 1x10^6 km, and many images are needed also during the closest passage (for instance the WAC could follow an immersion or emersion of the possible satellite). Furthermore, the WAC images will always cover the entire asteroid, and will place the NAC images in the proper perspective.

Mission Phases: Global mapping and close observation

During the global mapping and close observation phases, the WAC will take close images of the comet that will cover a large portion of the nucleus (at a distance of 5 km from the surface, the FOV of WAC is 1.5x1.5 km^2 while NAC will cover 210x210 m^2). The WAC images will represent a reference frame on which to position the high-resolution NAC images.
It is not possible to define a priori the exposure times without knowing:
1) the albedo of the comet nucleus surface
2) the parameters of the orbit around the comet
3) the spin of the nucleus. The occurrence of smearing put strict constraints on the maximum exposure time.

Mission Phases: Comet escort to perihelion (extended monitoring)

After the deployment of the SSP, the spacecraft will spend about 8 months in a safe orbit around the nucleus until the comet's perihelion passage. In this phase the scientific goals of WAC will be to monitor the nucleus activity and take high sensitivity images of the nucleus environment. At a distance between 30-50 km from the nucleus, the FOV of WAC will cover a region up to 8 cometary radii. A wide range of flux intensities will be met in following the comet during its approach to the sun. Variable exposure times are then needed, from a maximum of about 200 msec at the beginning of the monitoring phase when the comet is at about 3 AU from the sun, to a minimum of 50 msec close to the comet perihelion using the filters with lower transmission coefficient

[Thunder82]

per chi vuole vedere le fasi della costruzione della Wide Angle Camera:

http://cisas.unipd.it/wac/images.html

[GioFX]

Originariamente inviato da Thunder82
Sono contento che il lancio sia andato bene!
Io faccio Ing. Aerospaziale qui a Padova. La facoltà è stata istituita da 3 anni, per rendere omaggio al Grande "Bepi" Colombo, professore ormai deceduto 20 anni fa dell'università di Padova che ha dato importantissimi contributi alla NASA nel campo della propulsione e la gestione dei veicoli spaziali (talmente importanti che la NASA gli dedicherà una sonda mi pare, è la prima volta che chiamano una sonda col nome di una persona...).

La BepiColombo è una missione destinata a Mercurio dell'ESA in collaborazione con la giapponese Jaxa, non della NASA.

[Thunder82]

Originariamente inviato da GioFX
La BepiColombo è una missione destinata a Mercurio dell'ESA in collaborazione con la giapponese Jaxa, non della NASA.

Vabbè, ho solo sbagliato organizzazione

Fattosta che è la prima missione a prendere il nome da uno scienziato contemporaneo mi pare

[GioFX]

Originariamente inviato da Thunder82
Fattosta che è la prima missione a prendere il nome da uno scienziato contemporaneo mi pare

In realtà c'era anche la missione, cancellata in novembre (per motivi di budget), Eddington. Cmq si, è una delle prime.

[baldoz]

A quanto ho saputo ci sono stati tagli di budget e il centro dell'ASI a Matera chiuderà... e così le partecipazioni dell'Italia alle missioni dell'ESA.
Un vero peccato!

[GioFX]

Originariamente inviato da baldoz
A quanto ho saputo ci sono stati tagli di budget e il centro dell'ASI a Matera chiuderà... e così le partecipazioni dell'Italia alle missioni dell'ESA.
Un vero peccato!

Guarda, non credo che chiudere un centro implichi non partecipare più a missioni internazionali. ASI non partecipa solo tramite ESA, ma anche come soggetto indipentente in missioni ESA e NASA.

[GioFX]

Two asteroid fly-bys for Rosetta

11 March 2004
ESA PR 15-2004. Today the Rosetta Science Working Team has made the final selection of the asteroids that Rosetta will observe at close quarters during its journey to Comet 67P/Churyumov-Gerasimenko. Steins and Lutetia lie in the asteroid belt between the orbits of Mars and Jupiter.

Rosetta's scientific goals always included the possibility of studying one or more asteroids from close range. However, only after Rosetta's launch and its insertion into interplanetary orbit could the ESA mission managers assess how much fuel was actually available for fly-bys. Information from the European Space Operations Centre (ESOC) in Germany enabled Rosetta's Science Working Team to select a pair of asteroids of high scientific interest, well within the fuel budget.
The selection of these two excellent targets was made possible by the high accuracy with which the Ariane 5 delivered the spacecraft into its orbit. This of course leaves sufficient fuel for the core part of the mission, orbiting Comet 67P/Churyumov-Gerasimenko for 17 months when Rosetta reaches its target in 2014.

Asteroids are primitive building blocks of the Solar System, left over from the time of its formation about 4600 million years ago. Only a few asteroids have so far been observed from nearby. They are very different in shape and size, ranging from a few kilometres to over 100 kilometres across, and in their composition.

The targets selected for Rosetta, Steins and Lutetia, have rather different properties. Steins is relatively small, with a diameter of a few kilometres, and will be visited by Rosetta on 5 September 2008 at a distance of just over 1700 kilometres. This encounter will take place at a relatively low speed of about 9 kilometres per second during Rosetta's first excursion into the asteroid belt.

Lutetia is a much bigger object, about 100 kilometres in diameter. Rosetta will pass within about 3000 kilometres on 10 July 2010 at a speed of 15 kilometres per second. This will be during Rosetta's second passage through the asteroid belt.

Rosetta will obtain spectacular images as it flies by these primordial rocks. Its onboard instruments will provide information on the mass and density of the asteroids, thus telling us more about their composition, and will also measure their subsurface temperature and look for gas and dust around them.

Rosetta began its journey just over a week ago, on 2 March, and is well on its way. Commissioning of its instruments has already started and is proceeding according to plan.

"Comets and asteroids are the building blocks of our Earth and the other planets in the Solar System. Rosetta will conduct the most thorough analysis so far of three of these objects," said Prof. David Southwood, Director of ESA’s Science Programme. "Rosetta will face lots of challenges during its 12-year journey, but the scientific insights that we will gain into the origin of the Solar System and, possibly, of life are more than rewarding."

[GioFX]

Rosetta's scientific 'first' - observation of Comet Linear

26 May 2004

ESA PR 29-2004. ESA's comet-chaser Rosetta, whose 10-year journey to its final target Comet 67P/Churyumov-Gerasimenko started on 2 March, is well on its way. The first phase of commissioning is close to completion and Rosetta has successfully performed its first scientific activity - observation of Comet Linear.

The commissioning activities, which started a couple of days after launch, included the individual activation of all instruments on board the Rosetta orbiter and the Philae lander. This first check-out worked flawlessly and showed that the spacecraft and all instruments are functioning well and in excellent shape.
The commissioning tests also paved the way for Rosetta's first scientific activity: observation of Comet C/2002 T7 (LINEAR), which is currently travelling for the first and only time through the inner Solar System and offered Rosetta an excellent opportunity to make its first scientific observation.

On 30 April, the OSIRIS camera system, which was scheduled for commissioning on that date, took images of this unique cometary visitor. Later that day, three more instruments on board Rosetta (ALICE, MIRO and VIRTIS) were activated in parallel to take measurements of the comet. Although the parallel activation of the instruments was not planned until later in the year, the Rosetta team felt confident that this could be done without any risk because of the satisfactory progress of the overall testing.

The first data from the remote-sensing observations confirm the excellent performance of the instruments. The four instruments took images and spectra of Comet C/2002 T7 (LINEAR) to study its coma and tail in different wavelengths, from ultraviolet to microwave. Rosetta successfully measured the presence of water molecules in the tenuous atmosphere around the comet. Detailed analysis of the data will require the complete calibration of the instruments, which will take place in the coming months. The OSIRIS camera produced high-resolution images of Comet C/2002 T7 (LINEAR) from a distance of about 95 million kilometres. The image (above) showing a pronounced nucleus and a section of the tenuous tail extending over about 2 million kilometres was obtained by OSIRIS in blue light.

The successful observation of Comet Linear was a first positive test for Rosetta's ultimate goal, Comet 67P/Churyumov-Gerasimenko, which will be reached in 2014. Rosetta will be the first mission to undertake a long-term exploration of a comet at close quarters whilst accompanying it on its way towards the Sun.

The unprecedented in-depth study conducted by the Rosetta orbiter and its Philae lander will help scientists decipher the formation of our Solar System around 4600 million years ago and provide them with clues of how comets may have contributed to the beginning of life on Earth. In particular, the Philae lander, developed by a European consortium under the leadership of the German Aerospace Research Institute (DLR), will analyse the composition and structure of the comet's surface.

After Rosetta's first deep-space manoeuvres were carried out on 10 and 15 May with the highest accuracy, the first phase of commissioning is set to be completed in the first week of June. Rosetta will then go into a quiet ‘cruise mode’ until September, when the second phase of commissioning is scheduled to start. These activities, including the interference and pointing campaign, will last until December.

So the Rosetta spacecraft is well under way on its epic 10-year voyage, to do what has never before been attempted – orbiting and landing on a comet.


Image of Comet C/2002 T7 (LINEAR) showing a pronounced nucleus and a section of the tenuous tail extending over about 2 million kilometres. It was obtained by the OSIRIS camera on board Rosetta in blue light from a distance of about 95 million kilometres on 30 April 2004.

[GioFX]

European probe slings past Earth on long trip to comet

BY STEPHEN CLARK
SPACEFLIGHT NOW
Posted: March 5, 2005

The one-year old Rosetta comet chaser made a return visit to Earth Friday, flying by the planet to receive a boost to begin the long process of eventually sending the spacecraft on a trajectory to intercept the comet Churyumov-Gerasimenko in 2014.


While approaching Earth for the first of a series of fly-bys, Rosetta turned its navigation camera to the Moon, half lit by the Sun. This image was taken at 1510 GMT Friday when Rosetta was 265,997 miles from the surface of the Moon. Credits: European Space Agency, ESA/ESOC

Launched last March 2, Rosetta has now completed one revolution around the Sun in an orbit similar to that of Earth. Over the past year, European controllers have put the craft through a number of tests to verify the function of key systems and instruments, and no major problems were reported.

Rosetta made its closet approach to Earth at 2209 GMT (5:09 p.m. EST) as it passed 1900 kilometers above Mexico. The fly-by will send the spacecraft into a larger solar orbit that will take it past Mars for another one of these "sling-shot" gravity boost maneuvers in February 2007, followed by two more passes by Earth.

These planetary fly-by's save fuel that would otherwise have to be spent to propel the spacecraft toward its target comet.

Controllers switched on some of Rosetta's scientific instruments in advance of the close approach to carry out calibration measurements of the Earth and Moon. Navigation cameras were also successfully tracked the Moon during the fly-by to test their ability to track objects in space. These cameras will be responsible for the rendezvous with Churyumov-Gerasimenko and for tracking as the probe passes by a pair of asteroids later in the mission.

Rosetta also captured images of the Earth and Moon near the point of closest approach, but those pictures will likely not be available for a few more days.

The European Space Agency also sponsored a contest for amateur astronomers to take pictures of Rosetta as it passed close to Earth. It was expected that small telescopes could distinguish the craft's 100-foot solar panels, and possibly its high-gain antenna.

The fly-by also put Rosetta in position to be able to observe NASA's Deep Impact probe as it fires a small projectile into comet Tempel 1. The impact will reveal the comet's inner structure, and Rosetta will turn its instruments toward the comet to make additional observations.

Rosetta is planned to be the first spacecraft to rendezvous with and enter orbit around a comet. These primordial relics from the formation of the solar system are believed to harbor materials dating back as far as 4.5 billion years. Rosetta will also release a lander to explore the comet at the surface.

[gpc]

Bravo Gio, vedo che stai tenendo fede al tuo impegno... mi raccomando, continua per i prossimi anni a tenerci informati, eh, contiamo tutti su di te

[pegasoalatp]

io c'ero.

[pegasoalatp]

1 Summary of Activities
The reporting period covers three weeks of cruise, in which telemetry stored during solar conjunction was recovered and the spacecraft reconfigured to Near Sun Hibernation Mode (NSHM).
On 24th May the spacecraft entered Passive Cruise Mode, including transition to NSHM, telecommunications reconfiguration to MGA with low telemetry and telecommanding bit rates and configuration of all subsystems for the new spacecraft mode. This completed the activities related to entry in Passive Cruise Mode. Two more passes were taken on 25th and 26th May, to
confirm the correct behaviour of the new spacecraft mode. The spacecraft will remain in this low activity, low bit rate mode until the 26th July.
No payload operations were carried out in the reporting period. SREM was kept active in the background for the entire period, and configured for a lower data collection rate to cope with the reduced visibility periods and bitrates available during the incoming passive cruise period.
A total of 7 New Norcia passes of 8 hours commanding were taken during the reporting period.
TM/TC links with the OCC have been established for all passes.
NNO Pass
Date DOY Main Activity
808 16-May-06 136 Monitor pass - Solar Conjunction TM Recovered
809 17-May-06 137 Monitor pass - Prepare NSHMEntry
814 22-May-06 142 Monitor pass - Prepare NSHMEntry
815 23-May-06 143 NSHM Entry - TTC reconfigured to MGA-X, TM bit rate to 148 bps, TC bit rate to 250 bps
816 24-May-06 144 NSHM monitor pass
817 25-May-06 145 NSHM monitor pass
823 31-May-06 151 NSHM monitor pass
At the end of the reporting period (DOY 153) Rosetta was at 354.0 million Km from Earth (2.37 AU; one-way signal travel time was 18 min 58 sec). The distance to Sun was 209.8 million Km (1.40 AU).

2 Satellite Status
2.1 Platform
2.1.1 AOCS / RCS
The AOCS configuration at the end of the reporting period is (since DOY 144/2006, Near Sun
Hibernation Mode entry):
• AOCS in Near Sun Hibernation Mode / attitude control based on Thrusters
• Gyros: all IMPs OFF
• Reaction Wheels: all OFF
• Both ACMs ON
• Star Tracker A in use (since DOY 286/2005); STR B OFF. Both units with SW 2.8.
• Gyro-less estimator ON, gyro-stellar estimator OFF
• Auto-WOL Disabled (since DOY 137/2006).
On DOY 137/2006, the Auto-WOL function was disabled. This function had been kept enabled throughout the solar conjunction as a safety measure for the long periods without ground station contact.
The only reaction wheel offloading of the reporting period was executed on DOY 143/2006, over the New Norcia station. During this wheel off-loading, the wheels were commanded to low angular momentums, in preparation for their switch-off at Near Sun Hibernation Mode entry a few hours later.
On DOY 144/2006, the Near Sun Hibernation Mode entry activities were carried out as follows:
- Solar Array Repositioning
- Wheel Offloading to +-2.71Nms
- Reactivation of unused ACM
- Activation of gyroless estimator and transition to GLEP
- Update of the spacecraft inertia matrix
- Ephemeris update
The spacecraft dynamics at Near Sun Hibernation entry stabilised within the commanded deadband of 1 degree (half-cone) within 30 minutes from the transition as expected. The fuel consumption at entry was 11.11 g. The maximum angular rate at entry was below 0.00015 rd/s
(rate around the X axis). On DOY 146 the attitude control deadband was changed from 1 deg to 5 deg half-cone over the non-coverage period. It will be reduced over each weekly pass to improve the RF link conditions.
On DOY 144/2006, STR-A lost track. Within 4 seconds, the AOCS had successfully commanded the unit back into tracking mode. No indication of the cause for this tracking interruption could be found in telemetry.
The current GSEP guidance is set as follows (since DOY 130/2006):
Guidance flags: X Earth pointing, Y axis perp to SSCE, +Y South pointing
Earth direction bias: For Normal Mode: No bias (+X Earth pointing).
For SHM: bias of 20 degrees over +X in the X/Z plane

2.1.2 TT&C
The performance of the subsystem is nominal.
On DOY 137/2006, the S-band transmitter 2 and the S-band ranging transponder were switched off. These units had been activated from DOY 074/2006 to support radio-science measurements during the solar conjunction.
On DOY 143, the TTC subsystem was reconfigured to use the MGA-X for up- and downlink.
The TM bit rate was reduced to 148 bps and the TC bit rate to 250 bps to ensure positive link margins throughout the NSHM phase. This configuration is the baseline for Near Sun Hibernation, as the attitude deadband of up to 5 degrees in this mode prevent the use of the
High Gain Antenna.
The back-up transponder remains configured for S-band reception at 7.8 bps via LGA-F
Since the TTC subsystem is configured on MGA-X and low bit rates, the downlink signal has been extremely noisy when coherent, as shown in the figure below plotting the received signal Es/No on DOY 151/2006. The noisy part of the plot corresponds to periods where the signal
was coherent.
This behaviour has already occurred in flight: it is normally indicative of false transponder lock conditions on-board and clears after a few hours. However, this time, there is no indication of false lock conditions in the transponder telemetry and the behaviour persists. Two Cebreros
passes have been scheduled on DOY 157 and 158/2006 to possibly discriminate between ground station and spacecraft as the cause of this problem.

2.1.3 Thermal
The thermal behaviour of the spacecraft is nominal and stable. Its configuration is NSHM1 since DOY 144/2006.
As expected after Near Sun Hibernation Mode entry, the temperature of the spacecraft internal units, such as batteries, tanks, CDMUs, reaction wheels, has decreased by a few degrees.
Apart from this mode-related adjustment of the on-board temperatures, the spacecraft is slowly warming up as the Sun distance decreases.

2.1.4 Power
The subsystem is in its nominal configuration and performing nominally. All three batteries are in active configuration, at full state of charge.

2.1.5 Data handling
The subsystem is in its nominal hardware and software (v7) configuration. SSMM runs SW version 1.6 since DOY 159/2005.
On DOY 137, minor telemetry reconfigurations were performed in preparation for the upcoming Passive Cruise Mode phase. In particular, RPC events were re-routed from the default event packet store to the RPC event packet store to minimise the risk of an event packet store wraparound during the RPC observation of comet Honda, scheduled for beginning of July 2006 while
the spacecraft is in Passive Cruise Mode.
On the same day, the size of the packet store dedicated to Avionics dumps was increased to accommodate full SGM dumps performed outside coverage.
Systematic dumps of stored housekeeping telemetry were suspended at Near Sun Hibernation Mode entry on DOY 144. They will only be resumed after Near Sun Hibernation Mode exit on DOY 207. In the mean time, only stored events and acknowledgements packets will be retrieved by ground during each scheduled ground station pass.
On DOY 144, the SSMM dumps were started only for events and acknowledgement packets, but no VC1 frame was received for several hours. A housekeeping dump was finally commanded in addition to generate a continuous VC1 flow. This behavior is under investigation.
The TC Link Monitor timeout was set to 11 days (15840 min) on DOY 145.

2.1.6 Mechanisms
All mechanisms are performing nominally. On DOY 143, the solar arrays were commanded to
an optimum position and the Solar Array Drive Mechanism switched off at Near Sun Hibernation Mode entry. Apart from one ground commanded repositioning of the solar arrays on DOY 172, the Solar Array drive mechanism will remain off throughout the Near Sun Hibernation phase.
The HGA Pointing Mechanism is switched off and will remain off throughout the Near Sun Hibernation phase.

2.2 Payload
The only instrument operated in the reporting period was SREM.
SREM remains active in the background for radiation monitoring. SREM’s data collection rate was further reduced on DOY 142 to cope with the limited ground contacts during the near sunhibernation period.

3 Ground Facilities
3.1 Ground Stations
A total of 7 New Norcia passes were taken over the reporting period.
During the reporting period, several incidents at the New Norcia ground station caused temporary degradation of the service:
- On DOY 143, the High Power Amplifier (HPA) tripped off twice during the pass. After the second drop, the Low Power Amplifier was used instead of the HPA. Each time, a few frames were lost as the downlink signal went non-coherent. Also ranging data were lost due to the trip-off events.
- During the pass on DOY 143-144 (the first pass taken with Medium Gain Antenna and low bit rates), it was not possible to resolve ranging throughout the pass, despite several sweeps with HPA and LPA. Towards the end of the pass, ranging lock was finally achieved using the HPA with 21kWatts.
- Since the pass on DOY 143-144, large noise is being observed on the downlink signal when coherent. The noise is observed independently from the IFMS or Power Amplifier used. Cebreros passes are scheduled on DOY 157 and 158 to further investigate the problem.
- On DOY 152, the HPA suddenly stopped working during the pass. The unit was left down for investigation. A few frames were lost when the signal went non-coherent, and ranging data could not be acquired. This was due to a piece of hardware failing with the Power Amplifier. The problem was fixed during the next working day.

3.2 Control Centre
The RMCS supported all real-time activities successfully.
On DOY 150, the FTS was upgraded on ROMCA to support grouped POR delivery by RSOC.
Following this installation, at LOS on DOY 152, periodic errors were generated by the FARCgfts task on the server (ROMCA). The software support team immediately fixed the problem, which was due to the fact that the installed FTS is configured by default for MCS based on the new SCOS-2000 version 3.1 while ROMCA is still running SCOS version 2.4.
Testing of the new version of the RMCS software (v3.7), based on the Venus Express system and in turn on the new SCOS-2000 v.3.1, continued throughout the reporting period. This version, first installed on the E-chain (EQM Operations) on DOY 128, was installed on the Bchain
on DOY 136. Since then, spacecraft telemetry is routed to the B-chain in parallel to the Achain during all scheduled ground station passes. Furthermore, the spacecraft was successfully commanded from the B-chain on DOY 137. Migration of the A-chain is planned for the next reporting period.

4 Special Events
None

5 Anomalies
The following Anomaly Report was raised in the reporting period:
ROS_SC-111 Unexpected Behaviour of VC1 Dump at low TM Generation Rate and Bitrate

6 Future Milestones
The spacecraft will remain in Passive Cruise Mode until the 26th July 2006. In the entire period, the spacecraft will be monitored on the basis of weekly ground station passes.
Operations for the Mars swing-by (February 2007) will start in August 2006, with another payload passive checkout (PC3), an intense tracking campaign around the Trajectory Correction Manoeuvre (DSM-2) in September, and the first payload Active Checkout (PC4) in November/December.