What we have achieved with Anusat so far.
A large number of components used in Anusat are low cost components meant for consumer applications.
Many of these were bought across the counters from the Ritchie Streets and Kings Roads of India, and many others from the
Digikeys and Farnells of the world. The entire RF chain, the entire payload chain including the baseband and RF stages,
the data acquisition chain, bus management and the Telemetry and Telecommand chains were all built by us from such
low cost components. The ground checkout and validation systems too were largely built using low cost student evaluation kits.
There were no special ESD precautions, no special screening procedures, no special uninterrupted supplies while testing,
and no radiation hardening. Most of the devices chosen were of plastic package, and hardly any of them had space heritage.
Most of the design, testing and integration of the flight model subsystems (excluding the solar panel) were carried out
in a typical college lab type of environment.
We were not encouraged in all these compromises. But we had to resort to these as we were racing against time,
having lost some crucial time during the initial phase. However, we had one important mandate, and that was to make liberal
use of Commercial Off The Shelf (COTS) components for technology validation. We could use these for our design, provided we
tested them out tirelessly. And test them we did, a few hundred times in the nearly integrated condition. It is this exhaustive
testing, that enabled us to break free from the constraints of �space heritage�, �radiation hardening� and �strict quality�
regimes. Each of these compromises would have been considered suicidal in any big mission.
For the Bus Management Unit (BMU) we made use of commercial grade antifuse Actel FPGAs, microprocessors,
SRAMs and PROMs. We were apprehensive of radiation related SEUs, but till date, the results obtained from Anusat
indicate that radiation has hardly been an issue. Further, as part of the payload, we have used the commercial grade
reprogrammable SRAM based Altera FPGAs. Such FPGAs are hardly ever used in space missions since they are known to be
even more vulnerable to radiation damage. Further, these were devices in a tiny 672 pin BGA package, which make them
vulnerable even to vibration or vacuum conditions. These reprogrammable devices too have been operating very well
onboard Anusat. The PSK/PM modulation and the FSK modulation and demodulation operations have also been implemented
using FPGAs in combination with D/A converter and A/D converters and these have also been working well on board Anusat.
In addition to the store and forward data communications payload, we have some auxiliary payloads for
technology validation. These include the use of low cost commercial gyroscopes and magnetometers, and the design of GPS
receivers and Turbo Code receivers. The latter two involved a lot of original design and development effort from our students,
as these are normally bought out even by established players in the space field. Due to intermittent data reception from
the payload, we have not yet been able to validate any of the payloads. The indications so far are that while we might be able
to succeed in validating the store and forward payload, we are not hopeful of validating the auxiliary payloads. As we have
indicated elsewhere on this website, the mandate for Anusat is much bigger than just operating the payload, and that the
success or otherwise of such a mission cannot be judged solely based on the performance of the payload.
There are plenty of COTS components onboard Anusat, and the total Bill of Materials (BOM) of the Bus Management Unit,
Onboard Computer, communications and RF, and Payload subsystems is of the order of about 7000$. Six months of successful operation
in space, Anusat is sending out its expected signals and also accepting our signals. The experience we have gained
would be of value to those who are designing very low cost missions and missions with fast turn around times.