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SNAP-1
SNAP-1: The Mission

SNAP-1: The Mission

The SNAP-1 nanosatellite was designed to develop a modular, multi-mission nanosatellite bus (mass range of 10-10kg), to demonstrate the use of miniature electrical and mechanical COTS product technologies in space, and their use as autonomous robots for observing orbiting spacecraft.

SNAP-1 was designed and built as a low-cost research mission by a joint academic-commercial team at the Surrey Space Centre and at SSTL, funded entirely by SSTL.

 

SNAP-1 mission objectives


To provide a test-bed for novel micro-electronic technologies - in particular a new GPS navigation system, APS camera technologies and RISC processors.

To provide experimental data and imagery to the radio-amateur/amateur scientific communities.

To provide a vehicle for the education and training of students in spacecraft engineering at undergraduate and post-graduate level.  

The SNAP programme was aso intended to demonstrate the feasibility of using clusters of low-cost satellites that can fly in formation and conduct multipoint remote sensing.

 

SNAP-1 mission achievements


The first fully 3-axis attitude stablised nanosatellite.
3-axis stabilisation was achieved by a momentum wheel and magnetorquers as actuators and the attitude was sensed by a 3-axis magnetometer and sun sensors.  

The first nanosatellite with on-board propulsion demonstrating orbit control.

The first in-orbit images of another spacecraft from a nanosatellite.
In June 2000, SNAP-1 imaged the RUssian Nadezhda satellite as well as Tsinghua satellite in orbit shortly after deployment from the launcher.

The first successful use of GPS on-board a nanosatellite - used for orbit manoeuvring
SNAP-1 carried an SGR-05 GPS receiver, a butane propulsion system and a camera.  The GPS receiver was used to update the orbit as the propulsion system raised the orbit by 2.5km in a rendezvous experiment. 

First use of propulsion on a nanosatellite and first use of butane as a space propellant
SNAP-1's propulsion system weighed less than 0.5kg.  It was used to raise the orbit of the satellite by over 3km and propel it towards a rendezvous with another SSTL spacecraft (Tsinghua-1).  A total of 2m/s velocity change was achieved over 75 firings.  One of the novel features was that the system did not contain a conventional propellant tank - instead, the propellant was stored in titanium tubing bent into a triangular shape.  

 

SNAP-1 & Tsinghua-1 rendezvous experiment


SNAP-1 was the first nanosatellite to demonstrate in-orbit inspection of another spacecraft and orbit autonomous attempted rendezvous.  The SNAP-1 and Tsinghua-1 satellites (both SSTL spacecraft) were released from the Cosmos launcher in different directions specifically to avoid the possibility of accidental re-contact.  SNAP-1 ended up in an orbit about 2km below that of Tsinghua-1 and, being relatively light, suffered more from the effects of atmospheric drag than the much heavier Tsinghua-1.  This meant that, relative to Tsinghua-1, SNAP-1 dropped in altitude more quickly.  This was exacerbated by a very active sun (at solar maximum), causing the atmospheric density at 700km to be higher than normal.  SSTL measurements showed that on average, SNAP-1 was falling at about 10m per day with respect to Tsinghua-1.

SNAP-1 in the foreground, and Tsinghua-1

The micro propulsion system on-board SNAP-1 was first used to maintain altitude by overcoming the relative atmospheric drag effects, and then also to climb back up to an altitude about 1km higher than that of Tsinghua-1.  Most of the propellant was used for this climb in December 2000.  In this period Tsinghua-1 separated from SNAP-1 by more than 10,000km along their orbital tracks.  A long sequence of thruster firings was initiated under the automatic control of the On Board Computer, and the GPS navigation system was used to keep track of the orbital changes.  Over a period of 30 days, the thruster was fired about four times per day, giving a change in velocity (delta v) of about 10 cm/s per day.  In January 2001 SNAP-1 was higher than Tsinghua-1 with the gap closing.  In total the propulsion system raised the altitude of SNAP-1 by about 4km all done with just 32.6 grams of butane propellant.  At maximum separation, Tsinghua-1 and SNAP-1 were about 15,000km apart, but by means of the propulsion manoeuvres, SNAP-1 brought itself to within 2000km of its target.  Thus, whilst a true rendezvous was not achieved, the agility and manoeuvrability of SNAP-1 under automatic control was amply demonstrated, meeting its mission objective.  

 

SNAP-1 Imaging capabilities


Three wide-angle CMOS cameras, each with a 350 x 288 pixel detector, and each with a 90 degree field of view to cover an arc of 270 degrees.

A single narrow-angle camera (350 x 288 pixels) co-aligned with the centre wide-angle camera providing the capability of finer feature inspection.  






 

Satellite Data

Name:
SNAP-1

Customer:
SSTL

Mission:
Earth Observation

Mass:
6.3kg

Platform:
SSTL-10

Launch Data

Launch Date:
28 June 2000

Launch Site:
Plesetsk Kosmodrome, Russia

Launcher:
COSMOS-3M

Orbit:

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