Vol.3, No.4, 285-290 (2011) Natural Science
Copyright © 2011 SciRes. OPEN ACCESS
Detecting the light of the night sky in Mars
Nebil Y. Misconi*
College of Engineering University of Central Florida, Florida, USA; nmisconi@mail.ucf.edu
Received 10 February 2011; revised 3 March 2011; accepted 27 March 2011.
In this paper a new methodology is outlined to
detect the dust content in the Martian atmos-
phere during nighttime. In the previous Lander
missions to Mars, scientists were able to de-
termine the dust load in the Martian atmosphere
during daylight using spectral lines of the Sun.
Since the dynamics of Martian dust storms had
been determined to be very rapid changing over
times of hours and not days, it is imperative to
determine the dust load during nighttime, so
future astronauts to Mars can take protective
measures for their equipment. They can also
factor this effect for their planned activities
during daytime. The new methodology greatly
improves the classical method for determining
the extinction in the Earth’s atmosphere. The
classical method uses observations of bright
stars from which the optical depth,
total, can
then be deduced from the classical brightness
equation. The classical method succeeds rea-
sonably well at high elevation angles from the
horizon but fails dramatically at low elevation
angles. It also determines
total from the slope of
a plot of observed brightness of a bright star vs.
air mass at all elevations. The plot shows a
straight line at high elevations angles, which
then curves and becomes uncertain at low ele-
vation angles. The new methodology bypasses
this severe difficulty by simply eliminating this
plot, and by acquiring the brightness of a bright
star above the atmosphere (no extinction) and
compares it to the observed bright- ness of the
same star below the atmosphere at all eleva-
Keywords: Mars Nightsky; Bright Stars
Atmospheric Extinction in Mars’ Nightsky;
Detecting Atmospheric Dust in Mars;
Detecting Martian Dust storms During Night
This paper is the first step to build on for a technique
to be incorporated in future NASA Mars missions. The
main objective is to acquire information on the Martian
dust load and other atmospheric constituents in the at-
mosphere during nighttime. This, we believe, is an im-
portant information, since by knowing the dust load
during the night using instrumentation (described below)
by the astronauts, may give them the capability to pre-
dict the dust environment characteristics would be dur-
ing the following day. Another important point is that if
the astronauts know the dust load during nighttime, then
they would be able to shut some instruments down, and
take other protective measures. Obviously, if the dust
storm is intense enough to completely hide the stars then
it would render our method completely useless during
these times.
This technique can be accomplished by comparing
two sets of observations: one is to observe pre-selected
bright stars such as Vega from the landing site on Mars,
and the other is to observe the same stars from above the
atmosphere or space in general. It can be accomplished
using one instrument or two identical ones. Once the
bright stars intensity profile are taken—only once—from
space, then the magnitude of the star’s brightness as seen
by one or both of these particular instruments is estab-
lished, without any atmospheric extinction and once, and
for all.
To acquire information on the dust load in the Martian
atmosphere during nighttime would require the follow-
ing: the star tracking instrument must be pointed to a
preselected bright star (such as Vega), and record its ap-
parent brightness. The bright star must be preselected
according to the Martian night sky at the time of the
landing and thereafter so it has a high elevation (close to
the zenith). This high elevation will guarantee several
observations at different air masses so that the variation
in the star’s extinction as a function of air mass be re-
corded. It is also required that the instrument would fol-
low the star’s trajectory in the sky until it sets below the
horizon. This condition requires also that the instrument
either follow the star and make continuous observations,
N. Y. Misconi / Natural Science 3 (2011) 285-290
Copyright © 2011 SciRes. OPEN ACCESS
or take observations at fewer points along the star’s me-
ridian (if for any reason the continuous observations are
not possible).
As mentioned earlier, the new method requires that
the same instrument must make one observation of the
preselected bright stars above the Martian atmosphere i.e.
from space. These required observations from space can
be made during the flight to Mars, and if that is not pos-
sible (since instruments are not usually exposed to space
during the flight to Mars), then the space observation
could be made sometimes before the start of the mission.
For example, it can be made by the same instrument
from the Bay of the space shuttle or preferably onboard
the Space Station.
Once this methodology is established, its value will be
effective as a set of information necessary for future
astronauts to consider as part of their environmental
monitoring during their stay. It has the important value
as a complementary data to the daytime monitoring of
the dust load (using the Sun), and other interrelation-
ships that can be inferred. It would also be a continuing
activity on all future missions to Mars and a mainstay of
the monitoring routine. The need for such observations
is essential in order to have a complete picture of the
motions of dust storms in the Martian atmosphere. If the
Martian dust storms resemble those on Earth in nature
but larger in magnitude, then it is possible to deduce the
following, based on the experience gathered from ob-
serving bright stars from Earth. A dust storm during day-
time, if intense enough, would hide the sky’s blue color
and the Sun, and completely hide the stars during night-
time. This also means that the dust environment near the
ground is very heavy. The point to be made here is that
the way the sky appears gives an indication of how
heavy the dust load near the ground is.
Determining the dust extinction coefficient τeff on the
Earth atmosphere has been an ongoing effort for a very
long time. The use of bright star observations in deter-
mining this coefficient has a long history with an im-
pressive amount of data collected by Earth observatories
from various locals, and modeling analyses of this data
are abundant. The improvements of the new method
over the classical method of observations, analysis, and
results, are outlined below. The new method along with
its simplicity offers a great leap of improvement over the
classical method.
We envision that a Star Imager and Tracker (hereafter
SIT) instrument designed for the purposes outlined here
may be added to the lander’s package so that it makes
observations of the same bright stars from the landing
site. The SIT (with multi-filtering system) should have a
maneuverable mount so it can follow the star until it sets
below the horizon thus capturing the extinction suffered
by the star’s brightness as a function of air mass. The
bright stars must be pre-selected according to the Mar-
tian night sky at the time of the landing and thereafter so
it has a high elevation (close to the zenith). This high
elevation will guarantee several observations at different
air masses so that the variation in the star’s extinction as
a function of air mass be recorded.
The simple mathematical analysis outlined in the sec-
tion below would give direct information on the dust
extinction coefficient τeffective. This information would
compliment the information acquired on the dust load
during daylight, which were made by observing the Sun
from past Mars landers at eight low-transmission solar
filters, 443 671 880, and 990 nm [1], when such obser-
vations will be conducted again in future Mars missions.
Comparisons between daytime and nighttime would
obviously reveal any dramatic changes, or relatively
small changes.
Observing bright stars in the Martian night sky should
be better than from Earth due to the fact that there is no
light pollution as there is on Earth. From the Interna-
tional Mars Pathfinder (hereafter IMP) archives we
quote D. Dubov the following: “The camera can expose
for up to 32 seconds, which gives it a respectable low-
light capability”. Peter Smith reports: “that the Univer-
sity of Arizona have recently imaged Orion (the constel-
lation, not the nebula) and gotten good results.” We ex-
pect to image bright stars and planets during the mission
and can probably image Earth as well. Please note how-
ever, Earth is less than a pixel wide in the IMP.”
A more recent information regarding imaging Earth,
we quote D. Mittman from the Pathfinder archives: “We
have not yet received a good picture of Earth from our
landing site on Mars and probably won’t. The reason has
to do with one of the discoveries we’ve made since
landing on Mars: the atmospheric dust extends further up
into the atmosphere than first thought. This dust catches
the sun’s light before sunrise and lightens the sky early
in the morning. By the time Earth rises over our landing
site (about 2:30 AM mars-local solar time), the skies are
already beginning to brighten. Even if the sky were to
remain dark enough to take a picture of Earth, the morn-
ing clouds would almost always block our view.” These
two quotes should stress the fact that bright stars and
perhaps the Earth (if conditions are favorable) can in-
deed give us the needed information on the dust load
during Martian nighttime.
N. Y. Misconi / Natural Science 3 (2011) 285-290
Copyright © 2011 SciRes. OPEN ACCESS
Smith [1] used basically similar methodology to the
one outlined below. However it still followed the classi-
cal method in the sense that the Sun was not observed
above the Martian atmosphere with the same instrument.
This condition is absolutely necessary in our new meth-
od in order to generate accurate values of the extinction
coefficient by dust. Smith [1] found daytime opacities of
0.42 to 0.52 and found changes during the daytime i.e.
morning vs. afternoon, and evening. The IMP has also
been used to determine the optical depth at night by im-
aging the zero-magnitude stars Arcturus, Vega, and Al-
tair. However, they found higher optical depth at night
(0.75 +/ 0.04) than day, which they attribute to “The
high optical depth has meant that images through the
geology filters typically only provide around 250 counts
on these objects in the maximum exposure time of 32.76
s. However, the diopter filter, used to investigate the
magnets in the near field, has a much wider bandpass
and provides several times the signal at the cost of a
smeared image of the star.” They reduced 21 images of
the star Arcturus taken over several nights and an air
mass range of 1.0 to 1.7 which gave the above optical
depth figure. They also attribute the higher optical depth
at nighttime vs. daytime to the formation of water ice.
Historically, information on the aerosols in the lower
part of the Earth’s atmosphere (~ 45 km) is of prime
interest to both astronomers, and atmospheric chemists
and scientists, for different reasons. The classical method
used by astronomers to obtain information on the extinc-
tion coefficient caused by aerosols can be summarized
by the following: using a small telescopic photopo-
larimeter with a narrow-band filter, one bright star can
be observed until it drifts near the horizon, continuously.
The star’s path over the sky covers a range of elevation
angles having different air masses. The star’s brightness
from this data is then plotted vs. its elevation angle or
the respective air masses. A least squares fit to the data
would then result in a solid line where the data is linear
(higher elevations). The slope of this line is proportional
to the extinction coefficient of the atmosphere at the
time and local of the observations.
Using this classical method to remove the atmospheric
effects from astronomical observations, we use the zo-
diacal light (ZL) as a good example since it is a well-
observed phenomenon from space, and more extensively
from the ground. Ground-based observations of the ZL
from Hawaii, Tenerife the Canary Islands, and other sites
has been going on for decades using photopolarimeters
(see [2,3,4,5,6,7,8]). The difficulties encountered in the
ground-based observations of the ZL are one of separa-
tion from atmospheric and non-atmospheric contami-
nants. The atmospheric contaminants are airglow line
and continuum emissions, extinction (scattering and ab-
sorption) of the ZL by atmospheric particulates and
off-axis light scattered into the instrument. The non-
atmospheric contaminants are: bright stars in the field of
view (FOV), integrated starlight (ISL, light from stars
that cannot be resolved by the instrument), and diffuse
galactic light (light scattered by interstellar dust).
In the case of Rayleigh scattering the differences be-
tween the Earth atmosphere and the Martian atmosphere
must be taken into account (however it may prove to be
minimal) in the modeling techniques which serves to
separate this component from the residual aerosol com-
ponent. To give an example of data obtained on the at-
mospheric extinction coefficient using the classical
method, Figure 1 shows a broad-band (blue, green) mea-
surements of Vega, on 9/10, November, 1966, from Mt.
Haleakala, Hawaii [9]. If the data were linear with air
mass, the slope would be proportional to the extinction
The atmospheric extinction can be calculated from the
classical relation:
obs o
where Bo is the brightness of the star outside the atmos-
phere. In the old method described above, the graph of
log Bobs vs. the air mass m(Z) should be a straight line
from which both the extinction coefficient and Bo can be
determined. In reality, the best-fit line to the data is a
straight line only at small air masses (linear part of the
data). As air mass increases the data becomes non-linear
and the atmospheric extinction coefficient cannot be cal-
culated but rather estimated. The non-linear part at high
air masses is the part that gives information on the
dust/aerosol part in the atmosphere.
Our proposed method will measure Bo directly by ob-
serving the preselected star from space and Bobs by the
same imager at the Martian landing site. This measure-
ment is at the core of this new technique. So for each
m(Z), computed for the respective Z angle from the ze-
nith by using the Van Rhijn function for the landing site,
we will have the respective values of both Bo and Bobs
measured. This will give us directly without the need to
any plotting or measuring the slope of a best-fit line to
the data, which suffers from being non-linear at high air
masses. Thus, we can rewrite Eq.1 as:
ln lnln
obso eff
BB mZe
N. Y. Misconi / Natural Science 3 (2011) 285-290
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ln ln
o obs
and the only unknown term is
eff Includes Rayleigh scattering by the Martian at-
mospheric gases and mostly extinction by dust, which
we call
The new methodology outlined here constitutes a ma-
jor advancement in determining
eff very accurately. This
is so, since
eff will be determined directly from the ob-
servations using Eq.2 , and without recoursing to plots of
log intensity vs. air mass which then deduces
eff from
the slope of the best-fit-line of the data that is not linear
at high air masses (see Figure 1 for atmospheric Earth
observations). New plots can be generated, such as
eff vs.
m(Z), to obtain the variations of
eff at low and high air
masses. The data generated from these observations will
serve as a library of data of the dust load during night-
time. The atmospheric extinction has two components:
one is Rayleigh scattering which for Mars would mostly
be CO2 molecular scattering, and the second which is
more dominant is extinction by dust particles which we
In Earth atmospheric observations for example, Wein-
berg [9] made extensive observations of star extinction
from Mt. Haleakala, Hawaii during the years 1964 to
1968. From these observations, Weinberg [10] concluded
that there are no significant yearly changes of
res, how-
ever, there are seasonal variations that peak in April and
October, and low in January and July. Figure 2 shows
the aerosol extinction
res at 4760Å, as a function of time
between the years 1964 to 1968 [10].
As was obvious from the extinction observations made
at Mt. Haleakala, Hawaii, extinction due to the aerosol
content of the atmosphere shows no correlation with
local air temperature or humidity. It also showed that the
extinction coefficient for aerosols varies with wave-
length as δ
. The best-fit curve to the Hawaii
data gives = 1.98.
This method of deriving the atmospheric extinction
suffers from the fact that the incoming irradiance above
the atmosphere of the star is computed using observa-
tions made by major observatories. Assumptions must be
made of the magnitude of the star at each specific wave
Figure 1. Shows broadband (blue, green) measurements of Vega on 9/10 November, 1966 [15].
N. Y. Misconi / Natural Science 3 (2011) 285-290
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Figure 2. Shows the aerosol extinction coefficient
res at 4760 Å, as a function of time between the years 1964 to 1968 [15].
length of the narrow-band filters used in these observa-
tions by convolution of each star’s spectra. This will
introduce some serious errors in the analysis of the data.
The new method however, eliminates all assumptions,
interpretations, statistical analysis, and some modeling,
which profoundly affects the results sought.
The SIT instrument suggested here will be simple
rather than complex. The basic elements of the SIT are a
small (~5 cm in diameter) objective that is suitable for
observing bright stars only and with spectral capability
(i.e. filter wheel). A star tracking motor will be added so
the instrument can track the star in its apparent motion in
the nightsky.
There has been numerous activities along with re-
ported results using spacecrafts that went to Mars con-
cerning the dust profile in the Martian atmosphere. For
example, we site two references among others: one is
Hoekzema [11] and the other is: Smith D. Michael [12].
This paper outlines a new methodology to measure the
extinction of bright stars in the Martian atmosphere from
future NASA manned and unmanned missions. Thus
information on the dust column density in the Martian
atmosphere can be determined during nighttime. This
will compliment data already obtained on the dust col-
umn density during daytime from observations of the
Sun in the Martian atmosphere using special filters. The
new methodology outlined here can be accomplished
with the technology that exists today.
This research was supported by NSF Grant No. ATM -9220736.
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