Minimize NEMO-AM

NEMO-AM (Nanosatellite for Earth Monitoring and Observation-Aerosol Monitoring)

The NEMO bus represents a technology evolution to the UTIAS/SFL (University of Toronto Institute for Aerospace Studies/Space Flight Laboratory) GNB (Generic Nanosatellite Bus) — providing a foundation for future high-performance nanosatellites.

The NEMO bus has a primary structure measuring 20 cm x 20 cm x 40 cm and is capable of peak power generation up to 80 W. A minimum of 30 W is available to the payload. The high peak power generation enables the NEMO bus to support a dedicated state-of-the-art high speed transmitter. The NEMO bus is designed with a total mass of 15 kg, 9 kg of which is dedicated to the payload. It can be configured for full three-axis control with up to 1 arcmin pointing stability.

GNB missions developed at UTISA/SFL include AISSat-1 (launch July 12, 2010), UniBRITE/CanX-3A (launch 2011), BRITEAustria/CanX-3B (launch 2011), CanX-4 and CanX-5 (launch 2011), BRITE-Poland (launch 2011/12).

The first spacecraft to use the new third-generation bus technology is the NEMO-AM (Aerosol Monitoring), a nanosatellite designed to perform multispectral observations in the VIS spectral range. The objective of NEMO-AM is to detect the aerosol content in the atmosphere with a ground resolution of up to 200 m. The NEMO-AM nanosatellite is being built under a collaborative agreement between UTIAS/SFL and ISRO (Indian Space Research Organization). 1) 2) 3) 4)

ISRO will provide the scientific expertise and the science algorithm. The spacecraft will be controllable from two sites in the ground segment: SFL in Toronto and from an ISTRAC (ISRO Telemetry, Tracking and Command Network) facility in India, using SFL distributed ground station network technology.

Spacecraft:

The NEMO-AM spacecraft bus is specifically being designed toward a level of performance that will redefine the state-of-the-art for nanosatellites. With up to 80 W peak power generation, the bus is capable of providing a minimum of 30 W to the payload. The larger payload capacity of up to 9 kg opens numerous payload possibilities, and the bus can be configured with state-of-the-art downlink and three-axes stabilization with up to one arcminute of pointing accuracy. The NEMO-AM spacecraft with a total mass of 15 kg builds upon the heritage of the GNB hardware. 5) 6)

The NEMO-AM spacecraft includes the same subsystem complements as those of a GNB spacecraft, namely:

- ARM7TDMI computer with up to 512 MB storage and 2 MB of EDAC RAM

- Battery charge discharge regulators

- Current limiting power supply

- 100 Wh Lithium-ion battery

- 4 kbps UHF receiver

- 32 - 2048 kbit/s S-band transmitter

- Three-axes magnetometer and fine sun sensors

- Actuation: Magnetic torquers and nano reaction wheels

- Attitude control computers with an EKF (Extended Kalman Filter) capability

- Passive thermal design

- XPOD (Experimental Push Out Deployer) duo separation system.

The EPS (Electrical Power Subsystem) on the NEMO-AM requires a newly developed system capable of generating up to 60 W of maximum power to support the instrument.

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Figure 1: Illustration of the NEMO spacecraft (image credit: UTIAS/SFL)

Parameter

CanX-2

NTS

GNB

NEMO-AM

Spacecraft mass

3.5 kg

6.5 kg

7.5 kg

15 kg

Spacecraft volume

10 cm x 10 cm x 34 cm

20 cm x 20 cm x 20 cm

20 cm x 20 cm x 20 cm

20 cm x 29 cm x 40 cm

Peak power, 25ºC, BOL

2-7 W

4-7 W

7-9 W

80 W

Payload mass

1 kg

2 kg

2 kg

9 kg (4)

Payload volume

1000 cm3

1700 cm3

1700 cm3

8000 cm3

Payload power @ duty cycle

1-2 W @ 100%

2 W @ 20-30%

3-4 W @ 100%
6 W max

45 W @ 40% min
65 W max

ACS stability

~2º (1)

Passive

~2º (2)
~60”

~2º (2)
~60” (3)

Downlink

32 kbit/s-1 Mbit/s

32 kbit/s-1 Mbit/s

32 kbit/s-2 Mbit/s

32 kbit/s-2 Mbit/s (5)

Service
Launch

2008 (active)

2008 (active)

2010 (AISSat-1) active
Q1 2012 (BRITE)
Q3 2012 (CanX-4&5)



Q3 2012 (NEMO-AM)

(1) Nadir pointing with magnetometer,, sun sensor and one reaction wheel
(2) With magnetometer, fine sun sensor and three reaction wheels
(3) With star-tracker
(4) Including payload-specific equipment
(5) Using existing SFL transmitter;; NEMO has sufficient power for a 30 Mbit/s X-band transmitter at 20% duty cycle

Table 1: Comparison of UTIAS/SFL busses

NemoAM_Auto1

Figure 2: The NEMO-AM spacecraft and its components (image credit: UTIAS/SFL)

Payload volume

13,800 cm3

Payload power

15 W @ 100%, 60 W max

Spacecraft power

80 W max generation, 15 V bus, 160 Wh, Li-ion

Spacecraft structure

Advanced aluminum, magnesium, carbon fiber

Architecture

Scalable system with common technology and components,
Redundant connection and cross-strapping

RF communications

- Uplink: UHF (400-500 MHz), data rate = 4 kbit/s
- Downlink: S-band (2.2 GHz), data rate = 32 kbit/s to 2 Mbit/s

Computer

- Housekeeping, Attitude Determination and Control,
- Payload Computer: 60 MHz ARM7TDMI, EDAC RAM, 512+MB Flash

ADCS stability

2º with fine sun sensor, reaction wheels, 60 arcsec with star tracker, reaction wheels

Thermal control

Passive design; active control as needed

Propulsion

Optional: SF6 (cold gas), scalable for use with other chemical

Launch vehicle I/F

XPOD

Table 2: Summary of NEMO performance parameters

 

Launch: A launch of NEMO-AM as a secondary payload is planned for 2014 on a PSLV launcher of ISRO. The primary payload on this flight is SRE-2 (Space Capsule Recovery Experiment-2) of ISRO.

The secondary payloads on this flight are:

• IMS-1B (Indian Microsatellite-1B)

• CanX-4 and CanX-5, a pair of identical nanosatellites of UTIAS/SFL (University of Toronto, Institute for Aerospace Studies/Space Flight Laboratory), Toronto, Canada

• NEMO-AM (Nanosatellite for Earth Monitoring and Observation-Aerosol Monitoring), a nanosatellite of UTIAS/SFL.

Orbit: Sun-synchronous orbit, altitude = 635 km, inclination = 97.64º, period = 97.4 minutes, local time at descending node (LTDN) = 9:30 hours.

 


 

Sensor complement:

NEMO-AM carries an optical instrument (radiometer) capable of observing in the bands: 480-500 nm, 545-565 nm, and 605-625 nm (based on the channels on existing aerosol missions) with an optional observation capability in the NIR and SWIR (Short-Wave Infrared) bands. Two additional channels, 860-880 nm and 1580-1620 nm, have been considered and the 860-880 nm channel is currently being investigated for implementation.

The observation angle is the angle that is formed between the spacecraft the sun-target line and the sun-target line. The NEMO-AM attitude control system is designed to track a ground target position throughout a satellite pass. From the perspective of the target location this is from the point that the satellite rises above the horizon until it sets again below the horizon. This allows the instrument to observe the target from a variety of different observation angles and hence obtain differing measurements on the polarization of reflected light. The NEMO-AM is designed to make up to seven observations at the highest resolution at any observation angle that is possible as it passes over the observation area. The number of observations is dictated by the amount of data that can be downloaded.

The NEMO-AM instrument will also include a new instrument computer system. The new instrument computer will be responsible for controlling the operations of the multiple detectors. A four-channel observation at the highest observation comprising seven observation angles will generate up to 580 MB of data. The mission is designed to cover an area of up to 80,000 km2 daily. - The UTIAS/SFL-designed optical instrument is capable of a scalable ground sampled distance of 40 m to 200 m and a ground swath of 129 km from an orbital altitude of 650 km.

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Figure 3: Comparison of NEMOAM observation channels with those of current aerosol missions (image credit: UTIAS/SFL)


1) Freddy M. Pranajaya, Robert E. Zee, “The NEMO Bus : A Third Generation High-Performance Nanosatellite for Earth Monitoring and Observation,” Proceedings of the Symposium on Small Satellite Systems and Services (4S), Funchal, Madeira, Portugal, May 31-June 4, 2010

2) Freddy M. Pranajaya,, “Operational and Upcoming Nanosatellite and Microsatellite Missions,” APRSAF-16 (Asia-Pacific Regional Space Agency Forum), Bangkok, Thailand, January 26-29, 2010, URL: http://www.aprsaf.org/data/aprsaf16_data/Day-1_seu_1545_APRSAF-16_SEU-WG_Pranajaya_Microsatellite_and_Nanosatellite_Activities.pdf

3) F. M. Pranajaya, R. E. Zee, “The NEMO Bus: A Third Generation High-Performance Nanosatellite for Earth Monitoring and Observation,” Proceedings of the 24th Annual AIAA/USU Conference on Small Satellites, Logan, UT, USA, Aug. 9-12, 2010, SSC10-VI-8, URL: http://www.utias-sfl.net/docs/LivePapersAsOfJan2011/SSC10-VI-8.pdf

4) F. M. Pranajaya, R. E. Zee, “The NEMO Bus: A Third Generation High-Performance Nanosatellite for Earth Monitoring and Observation,” Proceedings of ASTRO 2010, 15th CASI (Canadian Aeronautics and Space Institute) Conference, Toronto, Canada, May 4-6, 2010

5) Freddy M. Pranajaya, Simon C. O. Grocott, Robert E. Zee, ”The NEMO Bus: An Advanced Nanosatellite Bus for Earth Monitoring and Observation,” Proceedings of the 28th ISTS (International Symposium on Space Technology and Science), Okinawa, Japan, June 5-12, 2011, paper: 2011-n-02

6) F. M. Pranajaya, S. C. O. Grocott, R. E. Zee, “The NEMO Bus: Nanosatellite for Earth Monitoring and Observation,” 8th IAA (International Academy of Astronautics) Symposium on Small Satellites for Earth Observation, Berlin, Germany, April 4-8, 2011; URL of presentation, IAA-B8-1401, http://media.dlr.de:8080/erez4/erez?cmd=get&src=os/IAA/archiv8/Presentations/IAA-B8-1401_Pranajaya_NEMO%20Bus.pdf


The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates.