L4 - Responsive Space & Small Satellites Flashcards
(16 cards)
What is Operationally Responsive Space? (ORS)
ORS will provide an affordable capability to promptly, accurately, and decisively position and operate national and military assets in and through space and near space. The ORS vision is to provide rapid, tailorable space power focused at the operational and tactical level of war.
What is the rationale behind Operationally Responsive Space?
The increasing international reliance on space systems justifies additional efforts to make them more robust. For example, natural hazards and man-made threats (debris, nuclear and RF weapons, cyber-attacks etc.…) to space systems are increasing; increased resilience is required simply to maintain current levels of resilience.
How can small satellites provide responsive space capabilities.
Deployed cheaper & faster.
Smaller daily response times.
High resolution (panchromatic for military)
Slew manoeuvres to increase it’s dwell time (time it “watches” over the same spot) and response time.
Can operate from any orbit. (=better revisits to regional users)
Track movements thanks to slew manoeuvres
What are the inconveniences of larger satellites?
Long settling times after manoeuvres in order to damp out vibrations which would otherwise ruin their images.
Give an example of a small satellite that demonstrates responsive capabilities.
➢ TopSat: launched in 2005, it carries out imaging with a ground resolution of 2.5 m. Much smaller and cheaper than other imaging satellites of similar high resolution, TopSat has been used to demonstrate the feasibility of providing images on demand to portable ground stations (e.g. on vans or trucks), such as that which might be deployed by the military or another disaster relief organisation. Record: from imaging to transmitting image back down: 20 min.
What is the Super Resolution Mode of a small satellite?
Satellite yaws and pitches backwards rapidly to allow smaller GSD (Ground Sampling Distance) both across and along track. Has the potential to deliver 40% improvement in baseline resolution.
What about taking videos with satellites?
hard in space cus high data rates, low resolution and requires extremely agile sat. But responsive sats can be used to improve those issues!
Cite all characteristics for a satellite to be considered responsive.
- Very high agility: pitch (allows them to reduce effective ground speed of the sensor, collect more light from a scene, produce higher quality images, maintain ability to image even if sun-synchronous condition degrades, permits images at night), yaw, roll (slew manoeuvre)
- Accurate pointing
- Be able to downlink data anytime
- High resolution (<5m): this results in a small swath width (typically ≤20km), but this doesn’t matter cus with a responsive sat you don’t want to map the world, you just want a quick picture of a targeted area.
If possible, however, there is considerable benefit in having both small-area, high resolution sensors and wide-area, medium resolution sensors on the same mission (e.g. SSTL-300) - Cheaper
- Launch on demand: is a key factor of responsive space, however the opportunity cost of having hardware on the ground is high (i.e. for launch on demand you need a stock of the product on the ground ready to be launched when required).
What is the main point of developing a constellation of small satellites?
Provide daily global coverage with a high resolution.
What would the ideal constellation of satellite be?
5 satellites in Sun Synchronous Orbit and 4 satellites at 40° inclination.
OR
4 satellites allowed to modify their in-plane phasing by 180°.
Describe a Disaster Monitoring Constellation.
5 sats, 30m resolution, daily global coverage, nadir pointing, 600km swath
Describe the RapidEye Constellation.
80 km swath, 6 m resolution, 5 sats and daily revisit times, roll capability of 45°
Cite one of the principal drivers for constellation design.
Need to make efficient volumetric use of the launch vehicle fairing.
Describe the next generation Earth-Mapper concept.
The entire land surface of Earth can be mapped on a daily basis by 5 satellites. If the ocean covers two thirds of the Earth’s surface, it is only one more iteration of Moore’s Law before we can cover the entire ocean surface on a daily basis. And one further iteration to cover the entire Earth’s surface on a daily basis. These design
Describe future military communication terminals.
Will need to rely on leading commercial technologies (small, mobile, low power, omni-directional, higher data rates, GPS anabled, low cost). Satellites links will support war fighters.
What technology will next generation platforms include?
- Intersatellite link system: Significant Implications for timeliness of data services, resilience through alternate communications paths, enhanced on board processing
- Enhanced on-board processing: offers speed of product delivery, reduction in data rates/bandwidth required, reduction in power required
- Use Very-Low orbits (i.e. <500km) to increase responsiveness (sacrificing lifetime).
