Thursday, March 31, 2016

EXOMARS, Trace Gas Orbiter & Schiaparelli

The objectives of ExoMars mission is to look for life beyond earth (exo-biology) and it is performed by sending an orbiter (Trace Gas Orbiter, TGO) and Lander (Schiaparelli) which is already on its way to the Red planet and preparing for a rover in the next available celestial window in 2018. It is a joint venture between ESA and Russian space agency Roscosmos. Instead of giving a routine information on this mission, I try to bring out the niche technologies utilized by the participating European countries in TGO, which are at the forefront of Planetary Exploration. Special emphasis is made to bring out those attractive aspects of the "suite of instruments" which are employed to hunt down the elusive secrets (methane) on Mars.

Courtesy: ESA 

Trace Gas Orbiter, as the name suggests is geared to look for trace gases, these are defined as the species which fall in "less than 1% composition" of a planet. Since the signature of life could be buried with methane, a trace gas, concentrations occurring at parts per billion (10-9) by volume; TGO carries a suite of instruments to monitor this gas primarily and many other trace gases which have been contemplated but never have been recorded at all. There is also an un-resolved issue of how the Martian atmosphere is lost; this could be accomplished by measuring ratios of isotopic species of various gaseous compounds with respect to the normal; example: HDO/H2O. By comparing the ratios with the one appearing earth; one can estimate the loss of lighter species as compared to heavy. In summary, the task of TGO is 1. to look for methane at ppb concentration levels (huge demand on sensitivity of the instruments) and 2. measure the ratios of isotopologus species (very high spectral resolution required) and 3. technology demonstration for landing in a thin Martian atmosphere (Schiaparelli).

A brief introduction on composition of Martian atmosphere:
Major gases [Martian atmospheric pressure ~ 10 torr (Earth's: 760 torr)]
CO2:  95%  (0.95)
N2 : 2.7%  (0.027)
Ar : 1.6% (0.016)

Trace gases
O2:  0.13% or 1.3X10-2
H2O:  2.0X10-4
CH4:  ~ 1.0X10-8 or parts per billion (10-9), (ppb)

For a composition analysing scientist measuring methane at a ppb level concentration is a million dollar ??? (or higher) question. This is where the Trace Gas Orbiter, TGO's journey to the red planet is holding huge expectations from the planetary scientists across the globe (which includes me).

There are 4-gem of instruments gear to break the technology barriers primarily geared in nailing down the elusive gas - Methane.
1. NOMAD (Nadir and Occultation for MArs Discovery)
2. ACS ( Atmospheric Chemistry Suite)
3.CaSSIS (Colour and Stereo Surface Imaging System)
4. FREND – Fine Resolution Epithermal Neutron Detector.

Each instrument's configuration and their scientific goals are nicely outlined here:

Courtesy, J.L. Vago, ESA
Both ACS and NOMAD are a set of spectrometers designed to measure a huge range of gaseous species (including isotopolagous), while CaSSIS is a color camera employed in imaging, FREND searches for H-atoms down to 1-meter looking for traces of buried water.

I spent 2-days in reading the "suite of instruments" NOMAD (Nadir and Occultation for MArs Discovery) carries and almost went MAD in appreciating the abundance amount of technological prowess this suite possesses. After debating on what proportion of "technical-popular" combination; I chose to take a middle path and try to keep the information flow in perspective so that both the casual and serious reader will be interested in reading beyond this paragraph.

Courtesy : ESA
(NOMAD instrument: 1. SO, 2. LNO, 3. UVIS, 4. Electronics)
NOMAD basically covers 0.2 – 4.3µ  spectral region with a set of 3-instruments operating in 3-different modes: 
1. SO: 2.3-4.3µ (Solar Occultation)
2. LNO : in 2.3-3.8µ (Limb, Nadir and Occultation) 
3. UV-VIS channel : 200-650 nm 

The SO mode is to look at the Sun during sunrise and sunset, while Nadir is looking straight down at the planet, LNO is a combination of limb scan /nadir view/Solar occultation. The table below is taken from a very recent publication of Robert et al appearing in Planetary and Space Sciences, outlining the greater details of what all NOMAD can deliver in different modes of observations.

Robert et al., Planet.Sp.Sc., 2016
Another notable point is the ability of NOMAD in detecting methane signal is given in the above said reference. Interestingly the NOMAD in LNO mode is capable of detecting methane even at 0.018 ppb (18 ppt) concentrations; which carries much superior sensitivity than the present day instruments both on Martian surface (CURIOSITY) and in the orbit (MOM: MSM, MENCA).

 Atmospheric Chemistry Suite is a kind of complementary, IR spectrometer again with a suite of 3- built-in instruments,covering a huge spectral region of 2.3 - 17µ  i.e. 1. NIR, 2. MIR and 3. TIRVIM.

Korablev, J.App. Remote Sensing, 2014

Just like NOMAD, ACS too has SO, Nadir and LNO observation modes explained in the above table.

The science goals of various sub-sytems are:

NIR instrument:
a. Monitoring and profiling of trace components, CO, H2O, O2
b. Vertical profiles of atmospheric density
c.  Sensitive search for new OH, O2 and NO night glow

MIR instrument:
a. Vertical profiles of СО2 (atmospheric density and temp.) ; minor species like CH4 , H2O, СО
b. Profiling of isotopic ratios HDO/H2O, 13CO2/CO2, CO18O/CO2

TIRVIM instrument:
a. Search/monitoring of minor constituents
b. Monitoring of atmospheric dust, and condensation clouds
c. Monitoring of the thermal state from the surface.

Most striking aspect of ACS is a huge spectral resolution (resolving power~ 50,000) it offers in the MIR region of 2.3-4.3µ. This would help in detecting the trace gas species first time ever: CH4, C2H2, H2S, HCl.  The TIRVIM region is helpful in:a. detecting trace gases, b. measurement of thermal profiles, c. aerosol properties and d. trace species: NO, N2O measurements.

The color camera's spatial coverage (swath) and resolution details are outlined here:

Courtesy: J.L. Vago, ESA

Artist's concept of the instreumnt and similar kind of observation made are given here:

Courtesy: J.L. Vago, ESA
TGO has added huge expectations among the Planetary scientists who are looking forward to fix the jigsaw puzzle on life beyond earth and in particular signatures of life on our next neighbour.

Saturday, March 5, 2016

India need Nano satellites; Future of Space Sciences

Sputnik 1 was the first human endeavour to leave mother earth (October, 1957) to be able to wander into Space. Though it was a small satellite ( ~ 83 kg), the later attempts by humans to explore space (Low Earth Orbit, LEO) were becoming increasingly bulky. The exploitation of geo-synchronous orbit (36,000 km) for beaming telecommunication and other signals could only add more burden on building huge work horses (Envisat ~ 8,000 kg). The present discussion is limited to Nano-Satellites, which fall in the 1-10 kg weight category; while Micro- satellites are in 100-10 kg and Pico satellites under 1-kg.

As the miniaturisation in electronic components (MEMS) started, so was the aerospace industry turning to COTS (Commercial, Off-the-Shelf) based small satellites. The idea was to try out newer technology riding on tiny satellites (Micro / Nano) even if the sub-components are not of very expensive MIL (military) grade, meaning radiation hardened class.  In came a "golden standard" called Cubesat, by a group of scientists lead by Bob Twiggs (Stanford Univ) and Jordi Puig-Suary (Calpoly University, California) in the year 1999. They called 1U (1-unit) which would measure 10 X 10 X 10 cm and weigh less than 1.33 kg. Same group also came up with a great idea of developing a P-POD (Poly-Pico satellite Orbiter Deployer) satellite dispenser. Their idea is to impart training for the undergrad students in the space technologies at affordable budget.

Credit : Skybox Imaging

The first Cubesat shot into space in 2003.. oh boy!! ... it transformed the land scape of how one reaches space.  The years 2014, 15 saw nearly 100-Cubesats launches each across the globe. In USA (and Europe) NASA, US-Air force ventured into Micro-satellite developmental programs. NASA's AMES centre had well laid program on Space biology, Lunar Sciences and Inter-planetary missions.  Similarly, JPL (Jet Propulsion Laboratory) too has a vibrant Cubesat program to monitor the earth and also a curious MARCO (Mars Cube One). MARCO's are two data relaying Cubesats which will be part of NASA's  next journey to Mars. They call it a "Technology Demonstration".

Observations made by Michael Swatwout at Saint Louis University, highlights the point (shown below) that the task of Nano satellites has tilted towards Technology demonstration as compared to Educational purposes. A country like India can afford to skip the FIRST step and take advantage of easily availabile components to be able to develop newer technologies.

Credit: Michael Swatwout, SLU

Nano-Satellites: Easy to make
It is not the big players for whom the tiny cubes were like TOYS, even for a lazy engineering graduate there are almost a dozen shops opened up in USA, where a stroke of key board and a credit card can bring him "Power board to Communication board even a Cubesat camera. Here are a few to quote as examples:

Credit: Cubesatkit

INDIA and Nano-Satellites
India has started venturing into space from the SLV (Satellite Launch Vehicle, 1979) Program. The first flight under the leadership of very well known face from India Dr. APJ Abdul Kalam was a failure; within a year the next flight roared into the skies of Sriharikota in southern India; that was lesson#1 in the history of ISRO; they never seem to look back in repeating failures. The PSLV (Polar Satellite Launch Vehicle) too had to face the setback in its first flight but never ever looked back till date... the present SUCCESSFUL FLIGHT number is 31 and is still counting.

As dictated by the priorities, the Indian Space Research Organisation (ISRO) has been having a very active, bright, successful program which has catapulted the country's name among the league of biggest players in world. ISRO has been successful in low earth orbit programs (IRS satellites), geo-synchronous orbit program and a very successful Lunar (Chandrayaan-I) and Martian (MOM) missions. Capturing the tag of FIRST nation to do so in its very FIRST attempt.


However, the neglected aspect of Small Satellite activity can be gauged by noting that India could launch a meagre number of FIVE in the entire history. Among these, there are just 3-of them which are 10-kg or less. Notable is JUGNU, a 3-kg satellite, developed by Indian premier education center: Indian Institute of Kanpur (IITK). The real hero in my view is STUDSAT which was developed by a group of engineering colleges from the cities of Bangalore and Hyderabad. The reason for STUDSAT to stand out is: due to their limited resources and also a mammoth task of co-ordination among the youth... Hats - off guys...

So... as my title says.... Today, India is a vibrant country with huge potential of growing in cutting edge technologies. Nano Satellites will offer a first hand training to the youth of our nation; also as it has been noticed worldwide that these tiny toys can serve as work horses for testing the new technologies in space, before venturing with millions of investments. With ISRO as the back bone, we can do a lot better than what we have been on the Nano Satellite front..... Let's kick start this activity.... which would bolster the Make in India program as envisaged by the central government.