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Draft:Milani

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Milani
Milani CubeSat inside the Tyvak International cleanroom
Mission typeDeep Space CubeSat and Asteroid orbiter
OperatorEuropean Space Agency
Websitewww.heramission.space/hera-mission-milani-cubesat
Mission durationPlanned: 6 months on orbit
Spacecraft properties
Spacecraft type6UXL CubeSat
ManufacturerTyvak International
Launch mass12 kg (26 lb)
Dimensions13 x 24.6 x 36.6 cm
PowerSolar array x 2
Start of mission
Launch date7 October 2024 (planned)[1]
RocketFalcon 9 Block 5
ContractorSpaceX
Deployed fromHera (space mission)
65803 Didymos orbiter
Orbital insertion2026
 

Milani is a CubeSat developed by Tyvak International together with a consortium of partner companies, universities, and research institutes from Italy, Finland, and the Czech Republic for the European Space Agency, to examine 65803 Didymos asteroid following Double Asteroid Redirection Test (DART) impact. Together with Juventas, it will be carried by the HERA mothercraft from the Low Earth Orbit to the Didymos binary system of asteroids, where it will be deployed to start its mission.

Milani was appropriately named after the Italian mathematician and astronomer Andrea Milani, a leading figure in Europe’s space science community, and a pioneer of asteroid risk analysis.​

Mission Timeline[edit]

Milani will be launched integrated inside the Deep Space Deployer (DSD) [2] in Hera, which will provide mechanical, electrical, and thermal housing for the CubeSat through the Cruise phase of the mission (2 years). The deployment occurs in a three-step deployment sequence, to be able to deploy and expose the spacecraft to the space environments, but remains attached to the Hera umbilical connection. Milani integrates the CubeSat Interface bracket (CIB) as structural element on the spacecraft, which allows supporting the exposed procedure, sustaining the shock loads during the deployment. On Hera, the CubeSat will be switched ON several times during the interplanetary Cruise phase, for the duration of the Stowed Health Check Test, which spans from 29 minutes to 45. Besides, the CubeSats will charge their batteries, to compensate for self-discharge, and keep safe states of charge.

After Hera performs its rendezvous and capture manoeuvre, and the preliminary characterization phase of the Didymos system, Milani will perform its final Stowed Check out tests, final battery charging, and Guidance Navigation and Control software updates (e.g. Didymos dynamical models, gravitational models, or estimated mass models). Ground control will decide to initialize the sequence for the Hera Payload Deployment Phase (PDP). The deployment of the Cubesat occurs in a three-step deployment sequence (approximately 1 week apart each) that is supported by the Deep Space Deployer (DSD):

  1. In the first deployment step, Milani is deployed from inside the DSD into the “exposed” configuration. In this configuration, the CubeSat is mechanically attached to the DSD, and thus Hera, but already exposed to the space nvironment. The umbilical connection routed through the DSD still provides data and power between the Hera and Milani. The umbilical connection allows for the initialization of the CubeSat sensors and establishes an RF communication link between the CubeSat and Hera.
  2. After CubeSat initialization Exposed checkout and inter-satellite Link commissioning are confirmed from the ground, and the umbilical connection between Hera and the Milani is removed by ground command. The umbilical release is trigged via a dedicated command by HERA to the DSD, this configuration is referred to as “released”. In this configuration, the CubeSat is mechanically attached.
  3. In the last step, the Milani is deployed from Hera S/C with the following release conditions: relative velocity to Hera equal to 3 cm/s with +/-1 cm/s dispersion and relative velocity direction error below 5 deg. The configuration after mechanical separation is referred to as the “Separated” configuration

Spacecraft[edit]

The Milani CubeSat is a 6UXL spacecraft [2] of 13 x 24.6 x 36.6 cm, with a weight of 12 kg. Its energy is provided by deployable two solar arrays. It is 3-axis stabilized and the attitude is maintained by 3 reaction wheels, 4 sun sensors, one star tracker, one inertial measurement unit and two cold gas propulsion systems.

View of the Milani CubeSat instruments
View of the Milani CubeSat instruments

The development of the spacecraft has been carried out by a consortium[3] of partner companies, universities, and research institutes from Europe:

Propulsion[edit]

Milani is equipped with two IANUS cold gas propulsion systems, developed by T4i in collaboration with Tyvak International. They provide up to six degrees of freedom, can be used both for attitude control and orbit manuevers.

Autonomous Navigation[edit]

The spacecraft is also equipped with a navigation camera [4] developed by the collabroation between Tyvak International and the Deep-space Astrodynamics Research & Technology (DART) Group of the Politecnico di Milano, that will help Milani to autonomously navigate and perform scientific operations. A LIDAR is also present on the satellite, and considering the relatively small range, it is complementary to the primary NavCam.

Inter-Satellite Link (ISL)[edit]

Once released, communication between ground and Milani would be achieved through an Inter-Satellite Link between Milani and Hera [4], using the mothercraft as data relay.

Scientific Payloads[edit]

Volatile In-Situ Thermogravimetre Analyser (VISTA)[edit]

The secondary payload on Milani is the Volatitle In-Situ Thermogravimetre Analyser (VISTA) developed by INAF which will accomplish the following scientific goals [2]:

  • Detect the presence of dust particles smaller than 10 μm (residual dust particles)
  • Characterization of volatiles (e.g., water) and light organics (e.g., low carbon chain compounds) by using TGA cycles. i.e. heating controlled thermal cycles
  • Molecular contamination monitoring onboard the spacecraft

Hyperspectral imager (ASPECT)[edit]

The ASPECT payload is a hyperspectral imager, developed by VTT operating in the visible and infrared parts of the electromagnetic spectrum. ASPECT imager covers [2] the wavelength range of 500 - 2500 nm and has imaging capability between 500 and 1650 nm. The imager is split into three channels: VIS (500-900 nm), NIR (850 - 1650 nm), and SWIR (1600 - 2500 nm).

The scientific goals of ASPECT are:

  • To map the global composition of the Didymos asteroids
  • To characterize the surface of the Didymos asteroids
  • To evaluate space weathering and global shock effects on Didymos
  • To identify local shock effects on Dimorphos caused by DART impact
Imaging characteristics of ASPECT
Channel VIS NIR1 NIR2 SWIR
Field of View [deg] 10 x 10 6.7 x 5.4 6.7 x 5.4 ca 5.85 circular
Spectral range [nm] 500 – 900 850 – 1250 1200 - 1600 1650 - 2500
Image size [pixels] 1024 x 1024 640 x 512 640 x 512 1 x 1
Pixel size 5.5 µm x 5.5 µm 15 µm x 15 µm 15 µm x 15 µm 1 mm x 1 mm
No. spectral bands Ca. 14 Ca. 14 Ca. 14 Ca. 30
Spectral resolution [nm] < 20 < 40 < 40 < 40

References[edit]

  1. ^ "Hera". ESA. September 2022. Retrieved 20 October 2022.
  2. ^ a b c d "AIT and System Level Verification for ESA Interplanetary Cubesats (Juventas and Milani), ready to piggyback on the ESA Hera Mission".
  3. ^ "CubeSat will sift asteroid secrets from reflected sunshine".
  4. ^ a b "The Hera Milani Mission".

External Links[edit]

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