'MAMBO Instrument in answer to CNES PREMIER …€¦ · Web viewFigure 2.1 Simulation of limb and...

PART 2: SCIENCE PLAN

Jet Propulsion Laboratory

Mars Atmosphere Microwave Brightness Observer

LERMA – LMDObservatoire de Paris - IPSL

MAMBOon MARS PREMIER

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Table of contents

2 SCIENCE INVESTIGATION PLAN......................................................................................................................5

2.1 Introduction.........................................................................................................................................................52.1.1 Why study the Martian atmosphere ?.............................................................................................................52.1.2 MAMBO and the Martian atmosphere...........................................................................................................5

2.2 Objective #1: Characterizing the 3D general circulation...................................................................................62.2.1 Scientific background.....................................................................................................................................62.2.2 Wind measurements........................................................................................................................................7

2.2.2.1 Science objective and requirements........................................................................................................................72.2.2.2 Retrieval of wind profile by MAMBO....................................................................................................................8

2.2.3 Temperature measurements...........................................................................................................................92.2.3.1 Science objectives and requirements.......................................................................................................................92.2.3.2 Retrieval of temperature profiles by MAMBO.....................................................................................................10

2.2.4 Combining wind and temperature: a complete view of the general circulation of the Martian atmosphere using data assimilation..............................................................................................................................................11

2.3 Objective #2: Characterizing the Water cycle..................................................................................................122.3.1 Water Vapor 3D mapping............................................................................................................................12

2.3.1.1 Scientific background............................................................................................................................................122.3.1.2 MAMBO objectives and science requirements.....................................................................................................132.3.1.3 Retrieval of water vapor profiles by MAMBO.....................................................................................................13

2.3.2 HDO 3D mapping........................................................................................................................................142.3.2.1 Scientific Background and objectives...................................................................................................................142.3.2.2 Science requirements.............................................................................................................................................142.3.2.3 Retrieval of D/H profiles by MAMBO.................................................................................................................15

2.4 Objective #3: Characterizing the photochemical state of the Martian atmosphere and surface.......................152.4.1 Scientific background and objectives...........................................................................................................15

2.4.1.1 Mars atmosphere photochemistry..........................................................................................................................152.4.1.2 Monitoring H2O2....................................................................................................................................................162.4.1.3 Monitoring O3........................................................................................................................................................162.4.1.4 Monitoring CO......................................................................................................................................................16

2.4.2 Measurements Requirements........................................................................................................................172.4.3 Retrieval of H2O2, O3 and CO.......................................................................................................................17

2.5 Objective #4: surface science...........................................................................................................................172.5.1 Scientific background...................................................................................................................................172.5.2 MAMBO surface observations.....................................................................................................................18

2.6 Science Implementation....................................................................................................................................182.6.1 Observing Strategy.......................................................................................................................................182.6.2 Data Scientific Analysis...............................................................................................................................192.6.3 Science team.................................................................................................................................................19

2.7 Relationship of MAMBO investigation to the other components of the Mars PREMIER 2007 program.......192.7.1 Synergy with Netlander................................................................................................................................192.7.2 Synergy with the “Escape Mechanism Package”........................................................................................19

2.8 Uniqueness of MAMBO compared to past, present and future missions.........................................................202.9 References.........................................................................................................................................................21





2 SCIENCE INVESTIGATION PLAN

2.1 Introduction

2.1.1 Why study the Martian atmosphere ?

The Mars Atmosphere Microwave Brightness Observer (MAMBO) aims to characterize the atmospheric dynamics, the water cycle and the photochemical processes of the Martian atmosphere with unprecedented measurements. The motivations for such an investigation are numerous:

o Understanding the present and past of planet Mars : More than ever, in the light of the current Mars spacecraft mission, we realise that the Martian atmosphere has played a central role in the evolution of the planet. Surface landforms tell us the story of a planet which has undergone climate change relatively recently and on which liquid water once ran in a distant past, making scientist wonder about a possible past life on Mars. However, complex photochemical processes seem to have now sterilized the near surface. Mars continues even today to exhibit major seasonal and interannual variations. The current Martian climate system is indeed a complex combination of atmospheric dynamics coupled with the dust, CO2 and water cycles. The behaviour of this system is not well understood, but it is the key to the history of the planet.

o Comparative meteorology and aeronomy. The general circulation of the Martian atmosphere is very similar to Earth, as both are rapidly rotating planets with relatively transparent atmospheres above a solid surface. Similarly, the chemical processes controlling the Martian atmosphere resemble the Earth middle atmosphere with, for instance, similar catalytic cycles controlling ozone in the middle atmosphere. The similarities and differences can help us better understand our planet and our environment. MAMBO will obtain a complete description of the time-varying properties of the atmospheric dynamics and composition in a systematic way analogous to modern observation systems in Earth orbit. It will thus enable us to perform comparative meteorology in an unprecedentedly detailed manner.

o Preparation of future missions. Another purpose of Mars atmospheric science is to better define the environmental conditions for future spacecraft missions: the goal is to facilitate spacecraft aerobraking and aerocapture manoeuvres, re-entry and surface operations of landers, or even the design of future balloons or planes. By measuring wind and temperature from the surface up to the altitude of aerobraking (~120 km), MAMBO is ideally suited for building the reference database that will be used by future mission designers.

2.1.2 MAMBO and the Martian atmosphereTo deal with the objectives mentioned above, we propose to analyse the thermal emission of the atmosphere at microwave frequencies using heterodyne spectroscopy, for the first time from orbit around another planet. In practice, MAMBO will perform measurements at the atmospheric limb and at nadir using a receiver dedicated to the monitoring of selected lines around 320-350 GHz (Figure 2.1). From these data, vertical profiles of key atmospheric constituents, of temperature and winds will be retrieved from the surface up to 120 km altitude with an unprecedented sensitivity and coverage, without being affected by dust or condensate. MAMBO beam size will be of the order of 8 km in our baseline design with a 23-cm antenna (possibly 6 km in our option with a larger 30-cm antenna). However, inversion techniques will allow us to a achieve an effective vertical resolution of only 5 km (3.8 km with the larger antenna) for water vapour and temperature retrieval.





2.2 Objective #1: Characterizing the 3D general circulationMAMBO will combine measurements of 4-dimensional fields of temperature and wind from 0 to 120 km.

2.2.1 Scientific background

As mentioned above, the concept used to describe the Martian atmospheric dynamics are close to the terrestrial case (see review in Leovy, 2001, Zurek et al. 1992). However, not much observational data are available. The temperature field has been the only global measurement used to characterize the circulation. In fact, only Mars Global Surveyor has really been able to provide more than sparse profiles measurements (Conrath et al., 2000 ; Smith et al., 2001) althought the main instrument used for this purpose (Thermal Emission Spectrometer, TES) was not especially designed for that goal. Within that context, our current vision of the circulation is largely based on numerical simulations performed using General Circulation Models (See Haberle et al., 1993, Hourdin et al., 1993, Wilson and Hamilton, 1996, Forget et al., 1999). In summary, these studies have shown that the global circulation is characterized by an extended Hadley circulation (a global cell with ascending branch in the summer hemisphere and descending branch in the winter hemisphere) modulated and modified by several kind of waves propagating through the atmosphere. Among these waves, of particular importance are the thermal tides of diurnal or semi-diurnal period which

are excited by the near-surface diurnal cycle and propagate through the atmosphere with increasing amplitude as the atmospheric density decreases with altitude (Zurek et al. 1992, Wilson and Hamilton, 1996). The tidal waves are thought to be the primary phenomena controlling the dynamics of the upper atmosphere above 50 km, although very few observations are available. With regard to comparative meteorology, the travelling planetary waves observed at high and mid latitudes in winter are of primary interest since they are the counterparts of the mid-latitude low- and high- pressure weather systems which control the weather in Europe and in Northern America.

Compared to the Earth, one key characteristic of the Mars atmosphere is the vertical extent of most meteorological phenomena. On Earth, the stratosphere confines the Hadley cell and most planetary waves to the troposphere, below 20 km. On Mars, there is no similar effect and many stuctures extend vertically up to the thermosphere (120 km), as suggested by MGS aerobraking desnsity measurements (Keating et al. 1998). Monitoring the global atmosphere from 0 to 120 km is thus of key importance.

Figure 2.1 Simulation of limb and nadir spectra around 320-350 GHz under typical martian conditions. MAMBO will simultaneously acquire complete spectra of the H2O, CO, 13CO, HDO, O3 and H2O2 rotational lines.

Nadir

Limbz = 10 km

Figure 2.2 Mars atmosphere General





Figure 2.3 A summary of the dynamical fields that will be observed by MAMBO, as simulated by a General Circulation Model (Forget et al., 1999) during Northern winter: temperature T, zonal wind U (eastward) and meridional wind V (northward). Mambo will mostly observe the zonal wind U , except at high latitudes when the spacecraft will fly above the pole.U is characterized by much larger velocities than V and is thus easier to measure. The middle and right columns shows the expected RMS amplitude of key meteorological phenomena thought to create day to day variability (transient waves) and diurnal oscillations (thermal tides). These phenomena are especially interesting above 70 km, where no global measurements will be obtained until MAMBO.

2.2.2 Wind measurements

2.2.2.1 Science objective and requirements

Except for the surface measurements performed by the Viking landers and Pathfinder, winds have never been observed on Mars by spacecraft. Until MAMBO, winds must mostly be derived from the temperature field using the thermal gradient wind approximation or more sophisticated similar techniques that assume zero velocity at the surface. However, such techniques may be far from accurate on Mars because of the near-surface winds driven by the strong diurnal cycle, and because of the large amplitude of the waves above 40 km and the difficulty of accounting for complex wave-mean interactions (Figure 1). For instance, a very limited number of Doppler shift measurements of the CO lines have been obtained using Earth-based radiotelescopes and interferometers (Lellouch et al., 1991, 1993, Moreno et al., 1999, 2001). These measurements suggest that retrograde winds around 60 km dominate at almost all latitudes, even around equinox (Jegou et al., 2000). This strongly disagrees with thermal wind estimates based on MGS TES data as well as with theoretical GCM predictions. The enigma raised by these remote measurements suggest that major findings in atmospheric dynamics relevant for both Earth and Mars science will be obtained by





MAMBO. To achieve a complete and accurate monitoring of the winds on Mars necessary to meet MAMBO objectives, the requirements on wind measurements are summarized in the following table:

WIND measurement specification

Requirements Requirements rationale MAMBO expected performance

Latitudinal coverage 0° to |lat| 75° Observation of winter jets and baroclinic waves (e.g. Figure 2.3)

0° to |lat| ~70°

Horizontal resolution(in latitude: lat)

lat 5° Scale of free atmosphere structures lat 3°

Vertical coverage 0 ≤ z ≤ 120 km Extension of main systems in models 15 ≤ z ≤ 110 kmLocal time coverage

Ideal

Descope

Coverage of diurnal cycle in 50 sols

A few fixed localtime

Mapping of diurnal cycle (tides) every Martian “months”

Sampling of diurnal tides

Only possible on a non sun-synchronous platform.

4 local times monitored by observing on both side of the sun-synchronous orbit.

Zonal or meridional wind ? Zonal Weakness of meridional winds Zonal winds at low-mid latitudeMeridional winds at high lat.

Accuracy U15 m/s Monitor mean flow + waves U15 m/s at 20 ≤ z ≤ 100 km

Vertical resolution z = 8-10 km 1 scale height z < 8 km

Table 2.1 Science requirements versus instrument performances for the wind measurements.

2.2.2.2 Retrieval of wind profile by MAMBO

The high spectral resolution achieved by MAMBO using heterodyne spectroscopy allows accurate line position and shape measurements. Winds can thus be measured remotely by observing the Doppler shifts of the emission lines that are narrow enough, in practice 13CO (between 15 km and 65 km) and 12CO (between 40 and 110 km). For a component of wind toward the spacecraft of 10 m/s, a spectral line formed in the region of the wind around 330 GHz will be blue shifted by 11 kHz. However, there is no need for such a high spectral resolution: the Doppler shift induces a change in the shape of the spectra which is easily detectable with a much coarser resolution (Figure 2.4).

Figure 2.4 : Detection of a 10 m/s wind Doppler shift by Mambo

In order to measure zonal winds at low and mid latitudes, Mambo will observe cross-track on each side of the near-polar satellite orbit. In such conditions, there are three source of errors that must be taken into account to estimate the expected performance of the instrument:

o Error due to the noise level: Figure 1.5 shows an estimate of the error induced by the instrument noise on the Doppler shift measurements performed with 13CO and 12CO . The use of

Doppler shift of a 13CO at 50 km (exagerated) Actual difference between 10 m/s

shifted spectra at MAMBO resolution,

Figure 2.5 Mambo wind retrieval performance for an observation time of 1s every 4 km(dashed line) and 10 s every 4 km (solid line). In practice longer integration time are obtained by averaging spectra. This estimation is based on Monte-Carlo simulations of wind retrieval performed by fitting model lines to the observed spectra.





both CO-isotope lines allows us to retrieve winds with an RMS accuracy better than 10 m/s between 20 km and 100 km.

o Error due to the spacecraft motion. The Doppler shift that results from the motion of the spacecraft relative to the planet can be as large as 4 MHz. This shift is reduced when looking to the side of the spacecraft, but the main error source is then related to the knowledge and stability of the spacecraft orientation. If the orientation of the spacecraft and the pointing direction of the telescope are in error by an angle , there will an unwanted Doppler velocity due to the spacecraft velocity Vspc equal to Vspc. The expected “3” attitude knowledge for the Mars Premier Spacecraft is 0.1° and the possible possible “3” error related to the stability of the MAMBO antenna pointing vector in the spacecraft reference can be estimated to be around 0.03°. For a spacecraft velocity Vspc = 3 km/s, the corresponding RMS error that must be quadratically added to the error due to noise is below 3 m/s.

o Error due to the absolute frequency calibration. The stability of MAMBO Ultra Stable Oscillator (USO) will be better than 10-8 and will allow a control of the reference frequency to 3 kHz, leading to systematic errors below 3 m/s. If needed, calibration of the frequency reference could be peformed by using Nadir spectra which should observe negligible wind velocities in the vertical.

2.2.3 Temperature measurements

2.2.3.1 Science objectives and requirements

An accurate measurement of the thermal structures of the atmosphere remains of primary interest in the study of planetary atmospheres and climates because: 1) Temperature is the main environmental parameter controlling the atmospheric density as well as physical processes (e.g. condensation) and chemical processes; 2) the signature of most meteorological phenomena can be analysed in the temperature structure; 3) the general circulation can be constrained from temperature measurements; 4) the knowledge of temperature is necessary to retrieve minor species. To achieve these objectives, the measurement requirements on temperature measurements are summarized in the following table:

Temperature measurement specification


Latitudinal coverage 0° to |lat| 80° Observation of polar warming and baroclinic waves (e.g. Figure 2.3)

Limb: 0° to |lat| ~70°Nadir: 0° to 90°


lat 5° Scale of free atmosphere structures lat 3°

Vertical coverage 0 ≤ z ≤ 120 km Extension of main systems in models 0 ≤ z ≤ 120 kmLocal time coverage As for the winds

(see Table 2.1)Monitoring of the strong diurnal cycle; sampling of diurnal tides

As for the winds (see Table 2.1)



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Accuracy & vert. resolution:- Vertical structure retrieval- General circulation :- Horizontal wave mapping:

T 3 K ; z=5 kmT 2 K ; z=10 kmT 5 K ; z=10 km

Wave, clouds (see Figure 2.3Haberle and Casting (1993), MEPAGModels (e.g. Figure 2.3)

See Figure 2.7See Figure 2.7See Figure 2.7

Table 2.2 Science requirements versus instrument performances for the temperature measurements.

2.2.3.2 Retrieval of temperature profiles by MAMBOMAMBO will retrieve temperature profiles from the 12CO and 13CO lines, the latter known to be 89 times less abundant. Compared to other techniques such as thermal infrared remote sensing, microwave temperature retrievals have the following advantages (Muhleman and Clancy, 1995):

o The observations are independent of the state of the atmosphere: Unlike in the IR, accurate profiles can be obtained for warm or very cold atmospheric conditions, during intense formations of atmospheric condensates or during intense dust storm conditions. These are, of course, conditions for which accurate temperature knowledge is most interesting.

o The inversion is simplified because of the good knowledge of the spectroscopic parameters, and because of the linearity with temperature of the thermal emission.

o The Local Thermal Equilibrium (LTE) assumption remains valid for rotational lines up to above 120 km (Non LTE processes are a major problem in the IR above 60 km).

Figure 2.7 : Left : Simulated performance (RMS retrieval accuracy, K) of Mambo in a typical martian case, for different vertical resolutions used in the retrieval .Right: Because temperature sensitivity decrease with altitude, the MAMBO standard product for each limb scan (every 3° latitude) will typically include one temperature profile from 0 to 120 km with vertical resolution of 5 km below 40 km and coarser above (Simulation performed with the MOLIERE optimal inversion scheme, Bordeaux Observatory).

The temperature will be retrieved simultaneously with the CO mixing ratio. In the lower part of the atmosphere, this dual retrieval will be facilitated by combining information from the weak line 13CO (more sensitive to mixing ratio) and the strong line 12CO (more sensitive to temperature). In any case, because of its long lifetime (>5years), CO is well mixed and its variations are expected to be small (these variations are

Figure 2.6 Impact of the vertical resolution on the restitution of a temperature profile showing a strong thermal inversion. (original data from the MGS radio occultation experiment, Hinson et al., 1999). Oscillations with similar scale, resulting from gravity waves, thermal tides or clouds are often observed on Mars. To capture such phenomenon, a vertical resolution of 5 km or better is necessary. MAMBO temperature retrievals will achieve 5 km (baseline design) and possibly 3.5 km with the optional (30 cm antenna).

Δz = 13km

Δz = 10 km

Δz = 5km





nevertheless interesting as explained in section 2.4). The error on the temperature induced by these variations should be small compared to the error directly due to the instrument noise, which are shown on Figure 2.7. Although the beam size of MAMBO will typically be 8 km, a better vertical resolution will be achieved by “oversampling” (e.g. acquisition of a spectra every 4 km). For each limb profile, the set of spectra transmitted by MAMBO will be inverted with various vertical resolutions, the coarser vertical resolution allowing a better accuracy (Figure 2.7).

2.2.4 Combining wind and temperature: a complete view of the general circulation of the Martian atmosphere using data assimilation

Temperature and wind provide complementary information about the general circulation of the atmosphere. Their combination will offer an unprecedented, complete view of Martian atmospheric dynamics. To make the most of these measurements, and to accurately interpolate them in space and time and build a detailed 4D climatology of the observed atmosphere, we plan to use a state-of-the-art data assimilation technique by which atmospheric observations that are non-uniformly distributed in space and time can be combined with simulations by numerical circulation models to provide optimal estimates of atmospheric transport. Such techniques are now systematically used on Earth to define the state of the atmosphere before performing weather forecasting or building reference climate databases (“analysis” or “re-analysis”). Since models of the circulation of the Martian atmosphere are analogous in their capability to their Earth atmosphere counterparts, data assimilation is readily applicable to Mars if enough observations are available (Lewis et al. 1996, Houben et al., 2001). Among the available techniques, we plan to use variational assimilation, a powerful technique initiated and developed by MAMBO co-investigator O. Talagrand at LMD (Talagrand and Courtier, 1990). Although our primary objective is to assimilate MAMBO’s temperature and winds, one advantage of variational assimilation is that it will be possible to take into account the information contained in the other observations (water vapour, CO mixing ratio) or even to directly assimilate the spectra rather than the retrieved quantities. Observations obtained by other instruments or missions (in particular, Netlander surface measurements) will also be taken into account.

2.3 Objective #2: Characterizing the Water cycle

2.3.1 Water Vapor 3D mapping MAMBO will obtain four-dimensional fields of water vapour from 0 to 60 km in all seasons and dust opacities.





2.3.1.1 Scientific background

Almost no profiles of water vapour have ever been measured on Mars. Nevertheless, the column abundance of water vapour in the Martian atmosphere has been monitored from orbiting spacecraft and Earth-based telescopes. The latest measurements from the MGS TES experiment have confirmed earlier Viking results and showed that Mars has an active hydrological cycle in which water is exchanged between the surface and atmosphere on seasonal and possibly diurnal time scales. With these observations, the only known surface reservoir for water is the residual north polar ice cap. To first order, every summer, water vapor is released into the atmosphere in the north polar region as the water-ice-covered northern permanent polar cap is exposed (Farmer et al., 1976; 1977; Smith et al. 2002). Water vapor is then transported southward by the atmosphere where it becomes available to form clouds and ice frost. No reservoir analogous to the northern ice cap has been detected at the south pole even though a high latitude summertime maximum also can be seen in the southern hemisphere. In this case, the source is likely to be water ice incorporated into the seasonal CO2 cap, or water desorbed from the regolith as the cap retreats and the surface warms. Both hemispheres are likely to have seasonal ice deposits and/or regolith water (Jakosky and Farmer, 1982). However, aside from the north residual cap, the distribution of exchangeable surface reservoirs for water is unknown. In fact, we do not understand the asymmetry of the water cycle and why water ice is currently stable at the north pole rather than at the south pole. This may result from the global north-south global elevation difference and its impact on the transport by the general circulation (Richardson and Wilson, 2002), or to the climate asymmetries induced by the variations in solar heating associated with orbital eccentricity. For instance, colder atmospheric temperatures during northern summer tend to lower the condensation level, and thus impede cross-equatorial transport (Clancy et al., 1996).

Understanding the water cycle is of key importance on Mars. The planet is replete with evidence suggesting variations in the nature of the water cycle over the planet’s history, including gullies formed by flowing water in the

recent past (Malin an Edgett, 2000, Costard et al. 2002). To understand the processes at work now and in the past, these processes must be observed in detail. In addition, recent observations suggest that water vapor and water ice may have a direct impact on the thermal structure of the atmosphere that is much larger than expected (e.g. Colaprete et al., 2000). It may also be an important process controlling the dust cycle and the global climate through dust scavenging.

Figure 2.8 : Seasonal changes in water vapor column abundance as a function of latitude (precipitable micrometers) as observed by TES aboard MGS (Smith et al., 2002) .Ls

is the solar longitude with Ls=0 at Northern spring equinox .Unlike TES, Mambo will be able to not only observe water vapour for column abundance lower than 0.1 pr-m , but to retrieve vertical profiles as well in such dry atmospheres.





2.3.1.2 MAMBO objectives and science requirementsMAMBO will measure profiles of water vapour over the planet with unprecedented sensitivity, and will allow these observations to be combined with 1) the local temperature profile at the same location and 2) the gobal determination of the atmospheric transport using temperature and wind measurements. In addition to providing a most detailed climatology of the daily evolution of water vapour on Mars, MAMBO will thus allow the quantitative characterization of water vapour transport in the atmosphere, and the potential identification of constant or time-variable source and sinks. By observing the dual variations of temperature and water vapour, we will study in detail the numerous physical processes involving water-ice thought to control the water cycle and the climate (condensation in the cross-equatorial cells, scavenging of dust by water, etc…). WATER VAPOR mea-surement specification


Latitudinal coverage 0° to |lat| 85° Observation of the northern (source) and southern (sink) residual polar caps

Limb: 0° to |lat| ~70°Nadir: 0° to 90°


lat 5° Scale of observed structures (clouds) lat 3°

Vertical coverage 0 ≤ z ≤ 60 km Extension of main systems in models 0 ≤ z ≤ 120 kmLocal time coverage As for the winds and T

(see Table 2.1)Monitoring of the strong diurnal cycle of water vapour proceses

As for the winds and T (see Table 2.1)

Vertical resolution Δz ≤ 5 km Resolution at condensation level Δz ≤ 5 kmAcuracy and sensitivity 0 – 40 km with

sensitivity 3%-30%See MEPAG report See Figure 2.9

Table 2.3 Science requirements versus instrument performances for the water vapor measurements

2.3.1.3 Retrieval of water vapor profiles by MAMBOWater vapour profiles will be observed with greatest accuracy at the limb. The H2O line near 325 GHz will be inverted to retrieve the water vapour mixing ratio using the temperature profile deduced from the CO and 13CO lines.

Figure 2.9 : Water vapour profile RMS retrieval accuracy for a typical atmospheric profile observed by Mambo : 17 pr-μm column abundance, well mixed below 10 km and saturated above. As for temperature, “over-sampling” the limb scanning allow to reach an effective resolution near 5 km, or better with the optional 30 cm antenna. However, the accuracy is better with a coarser resolution. Simulations have also been performed with an extremely wet (120 precipitable μm) and dry (<0.1 pr-μm) atmosphere. In the wet case, at low altitude, the line is completely saturated near its center, but the wideband spectrometers used by MAMBO permit the retrieval of water down to the surface by using the wings of the main line.”Oversampling” allows the achievement of a vertical resolution of 5 km,

2.3.2 HDO 3D mappingMAMBO will map the water vapour D/H ratio from 0 to about 40 km





2.3.2.1 Scientific Background and objectivesBy systematically mapping the profile of H2O vapor and its isotopic HDO species, MAMBO will map in 3D the space and time variations of the D/H ratio on Mars. Until now, only Earth-based telescopic observations have been used to detect HDO in the Martian atmosphere (Owen et al., 1988; Krasnopolsky et al., 1997; Encrenaz et al., 2001), with poor spatial resolution and seasonal coverage, and limited accuracy. Nevertheless, D/H ratios on Mars about six times that of Earth have been reported (Owen et al., 1988). This figure has been used to suggest that Mars has lost a significant amount of water (~50 m) to space through escape mechanism which tend to favour H escape compared to D. MAMBO will be able to set a reference value for the D/H ratio in the Martian atmosphere. However, our main goal is to monitor the strong variations of D/H that can be expected on Mars:

o Vertical variations: As stated by Fouchet and Lellouch (2001) and Bertaux and Montmessin (2002), the atmospheric condensation and thus the presence of water ice clouds creates a deuteropause; i.e. a level above which HDO vapor is strongly depleted. These changes occur because of the strong fractionation effect sustained by HDO during condensation process. Its lower vapor pressure forces it to be more concentrated in its icy phase (Merlivat and Nief, 1967). The objective of monitoring this process is twofold. First, model-data comparison will allow the determination of the separate roles of processes governing cloud stability and characterizing cloud microphysics. Second, we will be able to strongly improve our understanding of the D/H enrichment by escape processes and thereby constrain the volatile history. To first order, the ratio of the escape rate of D to H atoms is indeed proportional to the HDO/H2O ratio at the exobase level, which strongly depend on this poorly known “deuteropause effect”

o Seasonal and spatial variations: The seasonal condensation of approximately half the atmospheric water reservoir is expected to induce significant changes in the HDO/H2O ratio with time. In addition to the temporal signature of the seasonal cap formation, a horizontal gradient of the HDO/H2O ratio should appear off the polar regions. Within this context, HDO can act as a powerful tracer indicating the spatial origin of any air mass and the strength of dynamical processes governing the geographical distribution of water, thus constraining the global water cycle. A full year of tracking would also supply new information about the way isotopic equilibrium can be established when a large amount of water condenses. This has a particular significance for the volatile history.

o Local variations. It is possible that water originating from old reservoirs in the subsurface, or from

the old water ice on the northern ice cap, can exhibit a measurable difference in isotopic content relative to that of the atmosphere and the seasonally recycled northern polar cap frost. With the HDO/H2O ratio technique, we may be able to detect locations where such reservoirs are able to communicate with the atmosphere.

2.3.2.2 Science requirementsThe primary requirement is to retrieve HDO below and above the condensation level (e.g. 10-20 km) with sufficient accuracy to detect the expected [HDO]/[H2O] variations as shown in Figure 2.10 (right).





2.3.2.3 Retrieval of D/H profiles by MAMBO

Figure 2.11 Left: HDO profile RMS retrieval accuracy for a typical atmospheric profile observed by Mambo as in Figure 2.9, for vertical resolution 5 km and 10 km. Right: The red solid line show expected variations of the [HDO]/[H2O] ratio at condensation level, as simulated by Bertaux and Montmessin (2002). The error bar illustrate the typical accuracy of MAMBO retrieval for 1 limb scan (thin error bars) and after averaging 50 profiles (thick error bar). This error was roughly estimated assuming: δ([HDO]/[H2O]) = [HDO]/[H2O]) (δ[HDO]/[HDO] + δ[H2O] /[H2O]).

2.4 Objective #3: Characterizing the photochemical state of the Martian atmosphere and surface

MAMBO will measure 4-dimensional fields of key minor species: CO (0-120 km), H2O2 (0-30km), O3 (0-60km)

2.4.1 Scientific background and objectives

2.4.1.1 Mars atmosphere photochemistryThe photochemistry of Mars is rich, complex, and still poorly determined. Because of the limited surface pressure on Mars, photolysis of major (CO2: 95%, N2: 3%) and minor (H2O: 0.01%, O2: 0.1 %) molecular constituents extends to the very surface of Mars. This induces several catalytic photochemical cycles similar to the ones which control ozone in the terrestrial middle atmosphere, for instance. However, in the case of Mars these catalytic trace reactants seem to play a much more fundamental role related to the chemical stability of the bulk atmosphere. Without them, because three body recombination of CO and O from CO2 photolysis is an exceedingly slow reaction, the equilibrium composition of the CO2 Mars (and Venus) atmosphere should include much higher percentage levels of CO and O2 than is observed (~10% versus ≤ 0.1%).(Parkinson and Hunten, 1971 and McElroy et al., 1972). Other complex processes such as such as heterogeneous reactions on dust aerosols and surface condensation/adsorption of species like H2O2 remain conjectural. In this context of inferred and unknown behaviour, by observing the key lines characterizing all these photochemical processes MAMBO will effectively define the global character of Mars atmospheric chemistry for the first time.





2.4.1.2 Monitoring H2O2

H2O2 is among the most interesting species in Martian photochemistry. H2O2 has never been detected on Mars, but MAMBO sensitivity at the limb is such that we can safely plan to profile it and map its variations. o A key reactant: To confirm and detail the CO2 reforming processes mentioned above, none of the

key HOx radicals has been measured within the lower Mars atmosphere. It appears today that these hydroxyl radicals are mostly produced during the photolysis of H2O2. H2O2 is therefore the key trace constituent for the chemical regulation of H2, O2, and CO2.Global measurements of H2O2 vertical profiles in the context of simultaneous H2O, CO, and O3 observations constitute a major observational goal for the MAMBO experiment.

o A sterilizing oxidant in the Martian soil: The Viking Lander GCMS failed to detect any organic compounds in the near-surface, whereas other experiments revealed a reactive soil surface containing oxidant. The most likely candidate for a martian soil oxidant is H2O2 (Bullock et al.). Ground H2O2 would be produced in the atmosphere and diffuse into the subsurface over several meters. Understanding this process is of key importance for Martian exobiology.

2.4.1.3 Monitoring O3 As on Earth, ozone is another active species which abundance is controlled by complex catalytic photochemical cycles. Interestingly, three of the four major catalytic photochemical cycles which control ozone in the terrestrial middle atmosphere (NOx, HOx, and Ox; excluding only ClOx) constitute the primary photochemical families of the Mars atmosphere. The catalytic cycles of Ox (O, O2, and O3- products of CO2 photolysis) and HOx (OH, HO2, H2O2, and H- products of H2O photolysis) determine the distribution of Mars atmospheric ozone (O3), much as they do in the terrestrial upper stratosphere and mesosphere. In particular, Ozone is expected to be anti-correlated with water vapour. The simultaneous MAMBO will further explore the effects of saturation-induced (i.e., cloud formation) variations in atmospheric water vapor on Mars atmospheric chemistry. Because water photolysis supports the primary HOx cycle of Mars photochemistry, the extreme global-scale variations of Mars atmospheric temperatures force order-of-magnitude variations in HOx, NOx, and Ox abundances. This behaviour has long been appreciated with respect to factor-of-ten increases in ozone columns at winter high latitudes (Barth et al., 1973). However, the entire Mars atmosphere above 10-15km altitudes also exhibits comparable orbital variations associated with the 20K average atmospheric temperature variation forced by the eccentric Mars orbit (Clancy et al., 1995, 1999).

2.4.1.4 Monitoring COCO is a long-lived species. MAMBO will be able to characterize its source and sinks. However, an important objective for MAMBO photochemical measurements is to use CO as a tracer for Mars meridional transport: the weak meridional circulation of the terrestrial middle atmosphere is not directly observable, but appears as the mean transport effect of time-averaged eddies. By contrast, meridional circulation in the Mars atmosphere is reflected in a direct global wind field which has a fundamental but poorly understood influence on Mars climate. This includes the large north-south asymmetries of Mars polar caps and the formation of the polar layered terrains. Cross hemispheric transport of dust and water (vapor and ice) must play the primary role in these climate features, but their relative influence is difficult to constrain due to the complex character of coupled aerosol microphysics and transport. In addition to accurate H2O and zonal wind profiles, MAMBO will map the global distribution of CO mixing profiles. As shown by Joshi et al. (2001), the strong meridional circulation of Mars forces diagnostic vertical, meridional, and seasonal variations in CO abundance, which serve as an ideal tracer for Mars meridional transport.





2.4.2 Measurements Requirementso H2O2, O3 : Measurement of the H2O, O3, and H2O2 abundances (20% accuracy) from the surface

to the orbitally varying altitude of the hygropause (10 km at aphelion, above 40 km at perihelion) are required to define global CO + O2 recombination rates associated with HOx and Ox catalytic cycles, as well as the saturation-induced variations of HOx and Ox chemistry.

o CO: Retrieval of the CO mixing ratio to altitudes above 70 km (with 20% accuracy) are required to interpret meridional transport rates, based upon the preliminary GCM calculations of Joshi et al. (2001)

Both these criteria are expected to be fulfilled by MAMBO performances.

2.4.3 Retrieval of H2O2, O3 and CO

Figure 2.12: Simulated retrieval accuracy of minor species mixing ratio for an observation time of 1 s every 4 km (red dashed line) and 50 s (red solid line) relative to expected concentration profiles (black lines). In practice long integration times are obtained by averaging spectra. Comparison of the red and black line indicate that H2O2 will be retrieved up to 30 km on average, O3 up to 70 km, and that it will possible to monitor the source region of CO above 100 km.

2.5 Objective #4: surface scienceMAMBO will map the water ice content of the first millimetres of the soil, the surface roughness at a scale of a few tens of meters, and the seasonal polar cap characteristic in an innovative manner.

2.5.1 Scientific background MAMBO nadir measurements will include two cross-polarized continuum channel measurements in which the atmospheric line absorption will be negligible. They will thus measure the thermal emission of the near subsurface. The corresponding brightness temperature Tb is the product of two components, Tb = ε Ts with :

- Ts the vertically integrated physical temperature of the near subsurface (first millimetres). On Mars such a temperature can considerably differ from the skin surface temperature measured in the IR.





- ε the emissivity. For a given observation geometry, ε strongly vary with the surface roughness and the nature of the soil. When expressed in terms of brightness temperature, such variations are easy to detect.In the Martian case, the variations due to the nature of the soil should primarily results from the presence of water ice in the first millimetres (outside the seasonal CO2 ice caps), or from changes in the characteristics of the CO2 ice frost when observing within the seasonal caps. ε is also dependent on the viewing angle and of the polarization (see Ulaby et al. 1990).

2.5.2 MAMBO surface observations

MAMBO will use Horizontal (H) and Vertical (V) polarization, several viewing angles, and several local time observations to separate the variations due to 1) subsurface ice contents 2) surface roughness 3) CO 2 ice cap characteristic variations, and 4) variation of the temperature sensing depth.

In practice, Mambo will swept across the surface from limb to limb and measure the surface emission of about 20 points (see Figure 2.13) between the atmospheric limb observations (approximately every 6°latitude). Each point will be observed for 0.1s. The size of the corresponding field of view will be of the order of 3 to 6 km. With a bandwidth of 200 MHz, the brightness temperature will be measured with an accuracy better than 1 K.

2.6 Science Implementation

2.6.1 Observing StrategyMAMBO baseline observation strategy is described in Figure 2.14. In order to monitor the Martian atmosphere during one Martian year or more, Mambo is designed to operate during almost all phases of the mission (phase 1, 2a, 2b, etc.).

Figure 2.13: Emissivity polarization differences (V-H) on Earth at 85 GHz as observed by the SSM/I imager(Prigent et al. 1997). In the desert regions, this index is used to map the surface roughness MAMBO will obtain similar data, for the entire planet. At 300 GHz, it should be sensitive to surface rugosity scale of the order of a few tens of meters.

Figure 2.14 MAMBO Observing modes





In its baseline configuration, MAMBO will successively: scan one atmospheric limb on one side of the spacecraft orbit (off-track) between -10 and 130 km (0 to

120 km with margins) with a scan velocity of 4 km/s (total: 35 s). Spectra will be acquired every seconds observe the atmosphere and the surface near Nadir (3 points during 5s for the atmosphere + 20 points for

the surface, 0.1 s each). The viewing angles will be chosen to optimize atmospheric and surface science.

scan the limb on the other side of the spacecraft orbit like the first one. observe the “cold space” off the planet and an internal load for calibration purpose (see technical part). repeat the total sequence during a defined period.Taking into account transfer time for the antenna, the total sequence will last about 110 s. On average, one limb scan will be obtained every 55 s , thus about every 3° in latitude.

2.6.2 Data Scientific AnalysisThe scientific analysis of the Data will be first based on the traditional production of level 1 data (calibrated spectra), level 2 data (e.g. Wind, temperature, mixing ratio profiles), level 3 data (climatology, average, maps) and level 4 (assimilated data). Two kind of tools will be specifically developed for the operational data production:

o A 1D retrieval model. The employed retrieval method will be based on a state of the art "Optimal Estimation" scheme (Rodgers, 1976). Several teams may develop their own version, with a primary team based at Bordeaux Observatory using the MOLIERE (Microwave Observations LIne Estimation and REtrieval) tool originally developed to analysed the ODIN satellite aeronomy limb observations

o A data assimilation scheme which will be use to determine the atmospheric circulation from the wind and temperature measurements as explained in section 2.2.4.

On this basis, a large scientific team is gathered to address the numerous scientific objectives of MAMBO and use and interprete data from level 0 to 4. In particular General circulation / water cycle / chemical transports model are developed t o interpret the data.

2.6.3 Science team

The list of Co-Investigators is detailed in Volume 1.

2.7 Relationship of MAMBO investigation to the other components of the Mars PREMIER 2007 program

2.7.1 Synergy with NetlanderMAMBO observations will be of high interest for the Netlander mission: MAMBO atmospheric retrieval and characterisation of the atmospheric dynamic and transport will give

a context to the ATMIS meteorological surface measurements (T, wind, wave signature in pressure, water vapour variations). Conversely, ATMIS will provide a ground true for MAMBO

Similarly, MAMBO global assimilated dynamic field will allow to take into account the atmospheric somponent in the geodesic measurements of the NEIGE experiment.

Synergy with other instrument can be mentionned: camera (clouds, ground true for the surface roughness), near surface sensing experiment.





2.7.2 Synergy with the “Escape Mechanism Package”MAMBO observation will provide a context (i.e. atmospheric dynamic at 120 km) for the in-situ measurement performed in the thermosphere by the “escape mechanism package”. In addition, the D/H ratio measurements by MAMBO may contribute to our understanding of the escape mechanism above and provide some clues to explain the observations obtained by the package.

2.8 Uniqueness of MAMBO compared to past, present and future missions

Instrument Method Data Vertical resolution

Comments What MAMBO adds

Radio Science(most missions) Radio occultation Temperature

(0-40 km) < 2km Only a few profilesGood accuracy

Coverage, number of profiles, vertical extension (0-120 km)

IRIS (Mariner 9) IR spectrometer Temperature(0-50 km) > 10 km Only 20,000 spectra Number of profiles, vertical

extension (0-120 km)

TES (MGS) IR spectrometer

Temperature (0-60 km) > 15 km Designed for surface

scienceVertical extension and resolution. Accuracy

Water vapour(column) column Poor sensitivity at low

temperature

Vertical Profile; low temperature measurements, sensitivity and accuracy

Themis IR spectro-mapper Temperature(0-? km) ? Design for surface science Coverage, vertical extension and

resolution

PFS (Mars Express) IR-NIR spectrometer

Temperature(0-50 km) ~10 km Vertical extension and

resolution. Accuracy

Water vapour (column) column

Poor sensitivity at low temperature. Loss of sensitivity in dust storms.

Vertical Profile; low temperature measurements, sensitivity and accuracy

[CO] column Vertical profiling[HDO] column Vertical profiling

SPICAM(Mars Express

Solar occultation(UV)

Temperature(20-150 km) ~ 1km A few profiles Coverage, number of profiles,

lower atmosphere[O3](10-50 km) ~1 km A few profiles Coverage, number of profiles

Nadir sounding(UV + NIR)

[O3] column Vertical profile[H2O] column Only day side Vertical profile, accuracy

MCS(MRO 2005) Limb IR radiometer

Temperature(0-80 km) 5 km Sensitive to dust Vertical extension (up to 120 km)

insensitivity to dust, accuracyWater vapour(0-40 km) 5 km Sensitive to dust Better Sensitivity, accuracy,

insensitivity to dust

NoneWind measurement Never measured First measurement: MAMBO

[H2O2] Never observed First measurement: MAMBO

Table 2.4: Comparison of MAMBO’s performance with past, present and planned Mars atmosphere sounders





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